How can Paul identify as a preacher to the Gentiles when he was a former Jew?

Paul was indeed a Jew and devout Pharisee, but when God converted him on the Damascus road, God gave him a completely new gospel and doctrine. Have you ever considered why Paul never references anything of Jesus in his epistles? No teachings, no parables, no miracles. This is often a surprise to people! The ONLY thing Paul brings across into his epistles and into the grace gospel is the CROSS, which for the Kingdom gospel was a contentious issue according to Peter.

Gal 6:14  But God forbid that I should glory, save in the cross of our Lord Jesus Christ, by whom the world is crucified unto me, and I unto the world.

2Co 5:16-17 Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more. (17) Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.