Let's begin with the first question. Scripture is pretty straightforward about the Church's role in salvation, Its authority and Its organization.. You have an excellent command of Scripture and have probably been shown on multiple occasions by many freepers, those passages that support how Peter was chosen from among the 12 to shepherd the Church. Rather than repeat what others have said, I will summarize it with the following verses.
Matt 16:1 8 Peter was the Rock upon which Christ would build His Church. Matthew writing in Greek uses the masculine form of the word Rock (sometimes meaning "stone") rather than the feminine form to refer to Peter for very obvious reasons. However, since Jesus spoke Aramaic, the word He used to rename Peter was "Cephas," always meaning Rock (See John 1:42). Paul thus uses "Cephas" to refer to Peter throughout I Corinthians. So Jesus actually said to Peter, "Thou art Cephas and upon this Cephas I will build My Church." This did not make Peter or any of his successors sinless or free from personal error by any means. It means that Peter's teaching in all official capacities as head of the Church will represent the mind of Christ infallibly. Peter later denied Christ and even compromised the Gospel by his actions. Some later Popes fell into scandalous living, but neither Peter or these Popes introduced their errors into the Church as truth, as happened with Bishops at various times in every other center of Christianity in the world and in all Protestantism.
Matt 16:19 Peter also is made the Prime Minister of New Israel, the Kingdom of Heaven on earth. In the King's absence he would act with the full authority of the King, just as all prime ministers do. To Peter, Jesus said, "And I will give unto thee the keys of the Kingdom of Heaven: and whatsoever thou shalt bind on earth shall be bound in Heaven."
Isaiah 22:15-22 offers absolute proof Peter was being commissioned as Prime Minister by the King of New Israel to act in His authority in this world. Here King Hezekiah's Prime Minister Shebna is replaced by Elialcim and given the very same authority as was Peter in Matt 16:19. Peter's Primacy is also Manifest Throughout Acts though he was not the first to be chosen, nor the most spiritual.
In Acts 1:13-26, he led in the selection of Mathias the Apostle; 2: 14-41 led in the preaching on Pentecost; 3:6 7 performed the first miracle; 3:12-4:19 preached the second great message whereby 5,000 converted; 5:1-11 led in the first judgment in the Church; 8:14-17 opened the door of the Church to the Samaritans; 8:21 excommunicated the first heretic Simon Magnus; 10:44,46 opened the door of the Church to Gentiles; 15:7,19 brought a conclusion to the first council in Jerusalem and pronounced the first dogmatic decision. In all four listings of the Apostles, Peter's name is always first.
As for the pope's authority, as I mentioned earlier, it was given to him by Chirst - Matthew 18:18. God in His infinite Wisdom and Love, set in place a shepherd to resolve disputes. This authority was never questioned as evidenced by the many writings of the early christians. For example, the following was written by Pope Clement I to the Church in Corinth.
"Owing to the sudden and repeated calamities and misfortunes which have befallen us, we must acknowledge that we have been somewhat tardy in turning our attention to the matters in dispute among you, beloved; and especially that abominable and unholy sedition, alien and foreign to the elect of God, which a few rash and self-willed persons have inflamed to such madness that your venerable and illustrious name, worthy to be loved by all men, has been greatly defamed. . . . Accept our counsel and you will have nothing to regret. . . . If anyone disobey the things which have been said by him [God] through us [i.e., that you must reinstate your leaders], let them know that they will involve themselves in transgression and in no small danger. . . . You will afford us joy and gladness if being obedient to the things which we have written through the Holy Spirit, you will root out the wicked passion of jealousy"
(Letter to the Corinthians 1, 58–59, 63 [A.D. 80])
Is Apostolic Succession biblical? The role of apostolic succession in preserving true doctrine is illustrated in the Bible. To make sure that the apostles’ teachings would be passed down after the deaths of the apostles, Paul told Timothy, "[W]hat you have heard from me before many witnesses entrust to faithful men who will be able to teach others also" (2 Tim. 2:2). In this passage he refers to the first three generations of apostolic succession—his own generation, Timothy’s generation, and the generation Timothy will teach.
The Church Fathers, who were links in that chain of succession, regularly appealed to apostolic succession as a test for whether Catholics or heretics had correct doctrine. This was necessary because heretics simply put their own interpretations, even bizarre ones, on Scripture. Clearly, something other than Scripture had to be used as an ultimate test of doctrine in these cases.
Thus the early Church historian J. N. D. Kelly, a Protestant, writes, "[W]here in practice was [the] apostolic testimony or tradition to be found? . . . The most obvious answer was that the apostles had committed it orally to the Church, where it had been handed down from generation to generation. . . . Unlike the alleged secret tradition of the Gnostics, it was entirely public and open, having been entrusted by the apostles to their successors, and by these in turn to those who followed them, and was visible in the Church for all who cared to look for it" (Early Christian Doctrines, 37).
Here again, given our Lord's command to preach to all nations. In Matt. 10:1,40 - Jesus declares to His apostles, "he who receives you, receives Me, and he who rejects you, rejects Me and the One who sent Me." Jesus freely gives His authority to the apostles in order for them to effectively convert the world. Similarly, in Luke 10:16 - Jesus tells His apostles, "he who hears you, hears Me." When we hear the bishops' teaching on the faith, we hear Christ Himself.
In Acts 1:15-26, the first thing Peter does after Jesus ascends into heaven is implement apostolic succession. Matthias is ordained with full apostolic authority. Only the Catholic Church can demonstrate an unbroken apostolic lineage to the apostles in union with Peter through the sacrament of ordination and thereby claim to teach with Christ's own authority. Acts 6:6 - apostolic authority is transferred through the laying on of hands (ordination). This authority has transferred beyond the original twelve apostles as the Church has grown. Even Paul, who was directly chosen by the Risen Christ, only becomes a minister after the laying on of hands by a bishop (Acts 9:17-19)
We see in 2 Cor. 2:17 that Paul says the elders are not just random peddlers of God's word. They are actually commissioned by God. It is not self-appointed authority. And then in 2 Cor. 3:6 Paul says that certain men have been qualified by God to be ministers of a New Covenant. This refers to the ministerial priesthood of Christ handed down the ages through sacramental ordination. Sirach 7:29-30 reminds us that With all your soul fear the Lord and honor His priests. With all your strength, love your Creator, forsake not his ministers.. God is not threatened by the authority He gives His children! God, as our Loving Father, invites us to participate in His plan of salvation with His Son Jesus. Without authority in the Church, there is error, chaos and confusion.
So ... let's 'test' this by reading accounts from some of the early christians.
"And thus preaching through countries and cities, they appointed the first-fruits [of their labours], having first proved them by the Spirit, to be bishops and deacons of those who should afterwards believe. Nor was this any new thing, since indeed many ages before it was written concerning bishops and deacons. For thus saith the Scripture a certain place, 'I will appoint their bishops s in righteousness, and their deacons in faith.'... Our apostles also knew, through our Lord Jesus Christ, and there would be strife on account of the office of the episcopate. For this reason, therefore, inasmuch as they had obtained a perfect fore-knowledge of this, they appointed those [ministers] already mentioned, and afterwards gave instructions, that when these should fall asleep, other approved men should succeed them in their ministry...For our sin will not be small, if we eject from the episcopate those who have blamelessly and holily fulfilled its duties."
Pope Clement, Epistle to Corinthians, 42, 44 (A.D. 98)
"Hegesippus in the five books of Memoirs which have come down to us has left a most complete record of his own views. In them he states that on a journey to Rome he met a great many bishops, and that he received the same doctrine from all. It is fitting to hear what he says after making some remarks about the epistle of Clement to the Corinthians. His words are as follows: 'And the church of Corinth continued in the true faith until Primus was bishop in Corinth. I conversed with them on my way to Rome, and abode with the Corinthians many days, during which we were mutually refreshed in the true doctrine. And when I had come to Rome I remained a there until Anicetus, whose deacon was Eleutherus. And Anicetus was succeeded by Soter, and he by Eleutherus. In every succession, and in every city that is held which is preached by the law and the prophets and the Lord.'"
Hegesippus, Memoirs, fragment in Eusebius Ecclesiatical History, 4:22 (A.D. 180).
"It is my purpose to write an account of the successions of the holy apostles, as well as of the times which have elapsed from the days of our Saviour to our own; and to relate the many important events which are said to have occurred in the history of the Church; and to mention those who have governed and presided over the Church in the most prominent parishes, and those who in each generation have proclaimed the divine word either orally or in writing... When Nero was in the eighth year of his reign, Annianus succeeded Mark the evangelist in the administration of the parish of Alexandria...Linus ...was Peter's successor in the episcopate of the church there...Clement also, who was appointed third bishop of the church at Rome."
Eusebius, Ecclesiastical History,1:1,2:24, (A.D. 325)
Clearly, it was Christ’s intent to provide for an orderly succession of pastors to lead the church. That’s what apostolic succession is all about: it’s the unbroken chain from Christ to the apostles to their successors through the centuries, down to the present-day bishops of the Catholic Church. It’s important to note that the church doesn’t put these men over the Bible and Tradition. As the Second Vatican Council noted, these leaders are under the authority of God’s word and are subject to it, like every other follower of Christ (see Dei Verbum , par. 10). Their job is to serve the word of God by teaching and interpreting it so that we can take it as the guide of our lives without falling into all sorts of distortions. To exemplify this, those who watched the funeral of JPII will recall that when the casket came into view: a plain pine box, and on top of it, an open book of the Gospels with its pages fluttering in the breeze. This was a powerful statement about what leadership in the church is all about! Right there, atop the simple coffin, was the message: the pastors of the church are under the word of God. They are at the service of the word.
Wind blows the pages of the New Testament on the coffin containing the body of Pope John Paul II.