The big flaw in your mistaken understanding of Jesus, His Church and Israel is in the fact that Peter and the others not only accept and approve Paul, they embrace the revelations to him and include that in their preaching on Jesus.
Those Jews who did not reject Jesus, do not remain simply Jews, but the first converts to Christianity.
What you fail to see is that Paul is the first example of one called after the ascension of Jesus. The revelation to Peter regarding the Gentiles opens the door to the revelations to Paul.
In these successions of events, we see exactly what Jesus promised, that the Holy Spirit would lead them to all truth and thus, the workings of the Holy Spirit through the Church.
Now as for the Twelve Tribes, which you deny include the adopted sons and daughters. A view that is rejected by many Christian scholars and theologians, by the way.
It is interesting that James writes to the twelve tribes which are dispersed abroad. It is interesting because, 10 of the 12 are called the “lost tribes”. These lost tribes were subsumed/absorbed into the nations to which they were dispersed when they were conquered by the Assyrians. So, then why does James address his letter to them?
There is a whole lot more to all this than what you and others who believe as you do have focused on.
That is why it important to know and understand the Bible in complete synchronicity and not divide parts up to support error. To do so negates the what is said in the OT, what Jesus said, and even what Paul said.
I think we might get a better understanding of each other if you read my post 407. If I am speaking of LITERAL things, and you are speaking of SPIRITUAL things, we will never come to an understanding of God’s Word. For instance, will Peter and the 11 LITERALLY be seated on 12 thrones judging the LITERAL twelve tribes of Israel during the LITERAL Millenial Reign of Christ’s LITERAL Kingdom on earth? And so on..