If Paul's conclusion was that Jesus completed the law then... the problem ...
1. Why did Jesus' Disciples remain devout Jews after the crucifixion?
2. Why did Jesus make it clear in Matt. 10:5 that they [Disciples] were to go only to the Jews--the lost tribes of Israel?
3. Why did Jesus not inform the Disciples that he was sending Paul to them with this extremely important message?
4. Why wait so long after his [Jesus] death to do so?
5. Paul broke Jesus' commandments in Matthew 5:17-20.
6. If Paul's message was true ... why did it cause such a commotion--and an eventual falling out--between the two camps? It shouldn't have.
7. Why call Paul to Jerusalem (Jerusalem Council) on at least two occasions to answer charges by Diaspora Jews et al
that he was preaching abrogation of the Law?
My personal belief ... His [Paul] arrival on the scene, with a gospel that he claimed superior to that of the Disciples, caused a real bone of contention between the two camps. In fact, his message could easily be called heretical--and was. The Ebionites despised Paul, calling him an "apostate of the Law". The Diaspora Jews did the same--nearly beat him to a pulp (Incident at Antioch)!
The original Disciples--as mentioned above--had a serious problem with him as well, for Paul preached abrogation of the Law and broke Jesus' commandments in Matthew 5:17-20. Also, his personal theology (Galatians 2:2), obviously ruffled the feather of the pillars (James, Peter, John) of the Jesus movement. Again, and as you well know, they [pillars] called Paul (Who Paul called hypocrites!) to Jerusalem to answer various charges. The "Jerusalem Council" came to a tenuous agreement regarding the gentile issue, yes, but one that did not last. He eventually split with them ... and the rest his history.
1) Paul claims that his Gospel is from the risen Jesus and not from men--including the Disciples:
Galatians 1:16-19 I did not confer with flesh and blood, nor did I go up to Jerusalem to those who were apostles before me, but I went away into Arabia; and again I returned to Damascus. Then after three years I went up to Jerusalem to visit Cephas [Peter], and remained with him fifteen days. But I saw none of the other apostles except James the Lord's brother.
Galatians 1:11 The good news I preach is not a human message that I was given by men, it is something I learnt only through a revelation of Jesus Christ.
2) Paul goes to Jerusalem fourteen years later--fourteen!--and spends time with some of the Disciples and claims he learned nothing of worth from them:
Galatians 2:6 As for those who seemed to be important—whatever they were makes no difference to me; God does not judge by external appearance—those men added nothing to my message.
3) Paul claims his Gospel is the true Gospel, and that anyone who preaches otherwise are accursed, deceivers and liars:
Gal 1:6-9 I am astonished that you are so quickly deserting the one who called you in the grace of Christ and are turning to a different gospel- not that there is another gospel, but there are some who are confusing you and want to pervert the gospel of Christ. But even if we or an angel from heaven should proclaim to you a gospel contrary to what we proclaimed to you, let that one be accursed! As we have said before, so now I repeat, if anyone proclaims to you a gospel contrary [Galatians 1:11] (my emphasis) to what you received, let that one be accursed!
This, along with the bold statement that the Disciples "added nothing to my message," I think is clear evidence that Jesus did not appear before Paul with a new radical message to go to the Gentiles and did contradict Jesus' message.
Paul, a zealot if there ever was one, obviously had a profound theophany (out of profound guilt?). But his Gospel did not originate, nor was it accepted, by the Disciples. Paul states this himself! And there is even evidence that the Disciples sent out missionaries to counter Paul's teachings.