So you believe the gospel which Paul preached negates the gospel that Jesus preached? Do you understand progressive revelation? You need to learn how to rightly divide the word of truth. Don't allow your confusion to keep you from believing the gospel.
it is a nice post for the most part but I am not in agreement with the last part, I have a different view, a lot of people think Paul gave mysteries but it was explained way before by Jesus and the Old testament that Paul very frequently quotes not always naming his sources, what you mention about the disciples not understanding the resurrection is all true, Jesus through the holy spirit sent after his resurrection opened their understanding, for Paul, a well versed Pharisee he knew all this then from prophecy, Do not Forget that Jesus sent the disciples to the gentiles also, Peter was appointed by GOD to the gentiles, here is what Jesus said in the verses about the great commission in brief;
Mat 28:18 And Jesus came and spake unto them, saying, All power is given
unto me in heaven and in earth.
Mat 28:19 Go ye therefore,
and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
Mat 28:20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway,
even unto the end of the world.
The disciples were also sent to the gentiles at one point. This was known and was not a mystery, also about Peter the head of the church. For mat 28:20, t
he disciples were exceedingly fruitful, we have most of that Jesus did and was teaching and his Gospel in the Books of of Mattew, Luke, John ans Mark.
as for Peter appointed to the gentiles;
Act 15:7 And when there had been much disputing,
Peter rose up, and said unto them, Men and brethren, ye know how that a good while ago God made choice among us, that the Gentiles by my mouth should hear the word of the gospel, and believe.