Paul is very early, without benefit of connected stories of Jesus, without benefit of a developed Christology. Paul’s largely figuring it out as he goes.
Eph 3:1-5,
1 For this cause I Paul, the prisoner of Jesus Christ for you Gentiles,
2 If ye have heard of the dispensation of the grace of God which is given me [not to anybody else, including Jesus] to you-ward:
3 How that by revelation [not by Paul's own study of ancient texts or something] he made known unto me [not to anybody else, including Jesus] the mystery; (as I wrote afore in few words,
4 Whereby, when ye read, ye may understand [it is possible for you to know] my knowledge [Paul's knowledge, not Jesus'] in the mystery of Christ.
5 Which in other ages was not made known unto the sons of men [before Pentecost, including the gospels], as it is now revealed [when God revealed it to Paul, not to anybody else, including Jesus] unto his holy apostles and prophets by the Spirit;
What other ages? What did Paul mean by "now revealed?"
Clearly Paul was told something by God that nobody knew before God revealed it to him. Nobody in the gospels of Matthew, Mark, Luke, or John knew about this mystery (it's better translated as "secret").
As far as Paul having no contact with Jesus and therefore did not really understand things, that's patently wrong. Do you not believe that God inspired Paul to write what he wrote? Would God have needed a developed Christology before revealing the secret to Paul? I don't think so.
I know I keep asking you questions which you are kind enough to answer, so I hope you won't mind another one. What changed on the Day of Pentecost?
Be honest with yourself. Do you understand the mystery, the secret, God kept to Himself until He revealed it to Paul? It's critical to understand that secret if you are to truly understand what Jesus did for you.
Read the second chapter of 1 Corinthians. In the beginning part of that chapter Paul said he couldn't speak to the Corinthians about anything but Jesus and him crucified. In verse 6 and 7 we see Paul teaching something more than that to the mature ("perfect") believers. I'm afraid that if you don't understand the secret God gave to Paul, then you are among those whom Paul calls carnal and babes in 1 Corinthians 3:1. I hate to say that, but it's not really me saying it. God didn't inspire me to write 1 Corinthians! I'm just pointing out the obvious. Just read what's written.
There is a good book titled "The Purpose of the Ages" by John Lynn. From what little discussion you and I have engaged in, I can tell that you would be incredibly blessed by reading that book.