I really don't understand your reply, the same Polemics that Marcion espoused against practices of Jewish Law were later espoused by other Church Fathers as the Orthodox movement became more and more gentile.
Once again, the Romans didn't consider there to be any difference between the Jewish Sect known as "Christians" and other Jews.
And I suppose one day it's possible we may find evidence of another who quotes from Paul's epistles earlier than Marcion, but I think its interesting Justin Martyr never quotes from any of them. On what basis do you conclude that the Pauline epistles are in fact authentic?
I can see why you'd be confused.
A critical examination of history must seem like gibberish.
It may be interesting that Justin "never quotes Paul." But he quite obviously has a knowledge of Paul. This is so obvious in studies on Justin that I don't care to give examples. You can find that yourself.
I don't suppose that you've read the apostolic writings. I understand that Marcion is the so-called first person to quote Paul, but we don't even have any extant writings by Marcion -- they are only preserved in the writings of people who hated him. And Marcion didn't quote Paul - he preserved Paul's writings and edited them. Christians before Marcion copied Paul's writings as well. There are several examples of early Christians who use Pauline concepts, phrases, and such without saying "Paul said" - but then again, neither does Marcion.
Now Paul is dated from the Gallio stone, and his epistles are authenticated by the unity in vocabulary, syntax, rhetoric, and so forth.