"Moreover brethren I declare unto you the gospel which I preach unto you..."(1 Cor. 15:1).
"For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; and that He was buried, and that He rose again the third day according to the Scriptures." (1 Cor. 15:3,4).
THERE, for a start.
"Moreover brethren I declare unto you the gospel which I preach unto you..."(1 Cor. 15:1).
Nope. 1 Corinthians 15:1 does not say anything about sufficiency of Scripture and about the binding and non binding upon Christians.
"For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; and that He was buried, and that He rose again the third day according to the Scriptures." (1 Cor. 15:3,4).
Neither does this passage. Paul says that it is sufficient to good works, which is ironic given the hostility to the importance of good works (according to Scripture) that the Sola Scriptura crowd normally shows.
The Scriptures referred to in these passages is in fact the OT, which Jesus used to show that He is the Messiah.
How could Jesus have died and rose according to the NT Scriptures that had yet to be written?
Remember, when the letter to the Corinthians was written it was not considered scripture.