3 For this reason I, Paul, a prisoner for Christ Jesus on behalf of you Gentiles
2 assuming that you have heard of the stewardship of God’s grace that was given to me for you,
3 show the mystery was made known to me by revelation, as I have written briefly.
4 When you read this, you can perceive my insight into the mystery of Christ,
5 which was not made known to the sons of men in other generations as it has now been revealed to his holy apostles and prophets by the Spirit.
6 This mystery is1 that the Gentiles are fellow heirs,members of the same body, and partakers of the promise in Christ Jesus through the gospel.
Please note, verse 5.
St. Paul’s gospel, is that of Matthew, Mark, Luke and John, Peter, Phillip, Jude, James etc..
Furthermore, Paul states, CERTIFIES, that the gospel he preached was NOT preached before.
"But I certify you, brethren, that THE GOSPEL PREACHED OF ME IS NOT AFTER MAN. For I neither RECEIVED IT OF MAN, neither was I TAUGHT IT, but BY THE REVELATION OF JESUS CHRIST." Gal. 1:11,12. If it hasn't been taught to him by man, or received of him by man, then it isn't the same. Otherwise, why would Christ bother to give it to Paul by REVELATION? WHy not just send him to the 12 to be taught the gospel they preached?
Instead of letting God's Word plainly say what it says, you seem to be attempting to make it say something it clearly does not. The Scriptures you gave were about the Mystery, hid in God, from the foundation of the world. That we would be fellowheirs with Israel through the gospel. But you did not give us what that gospel is.