Uh, just a small comment. Paul never received further clarifications from James and Peter and John. They received clarification from Paul. (Gal. 2:1-14). As a matter of fact, Peter was rebuked by Paul.(Gal. 2:11). Paul could not possibly have gotten clarifications from them, as he received his message directly from the risen Christ. Not from man, neither was he taught it by man. But only by the revelation of Jesus Christ. (Gal. 1:11,12).
I was referring to the visits Paul made upon returning from missionary journeys, to talk with the Apostles. Paul indicated in his letters that he had sought to reinforce what he was teaching during his journeys. Perhaps ‘clarification’ was too loose a term.