He claimed to get his teachings directly from Jesus, a man who was dead and not there to talk to him.
Look, if you want to have faith in Paul, that's entirely your prerogative. For me, there are simply much simpler explanations than that he was channeling Jesus.
There are no Pauline scholars of note, whom I am aware of, that would endorse your contention that everything Paul tells us about Jesus came out of his own head from revelations.
We now know with relative certitude, based upon ample textual studies that in Corinthians, Galatians and Philippians he references pre-Pauline hymns and creedal statements. The famous statement: "
There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus" (
Galatians 3:28), has for now long been regarded by most scholars as a pre-Pauline baptismal formula. In other words, he didn't actually 'come up' with that profound insight - he simply inherited it from the Jerusalem church and was referencing what, by then in the 50s CE, was a common aphorism among the nascent communities of Jesus-believers used in their rituals.
Paul refers to his conversations with people who knew Jesus directly, including his brother James, the apostles Peter, John and others. He lived with the apostle Peter (Cephas) for fifteen days and we know that they were close enough to have engaged in a very heated argument that Paul boasted about many years after the fact. In both
Galatians 1:18-9 and
1 Corinthians 9:5 the “
brothers of the Lord” are mentioned.
Paul tells us he received the tradition (
paredōka = “I delivered”;
parelabon = “I received”), of Christ’s death on a Roman cross and burial. He reiterates this in
1 Corinthians 2:2,
Galatians 3:1,
2 Corinthians 13:4, and many more occasions. He didn't derive this from a "revelation" but from the same synoptic tradition we find in the gospels.
1 Corinthians 11:23-26 Paul tells us that he received the tradition that Jesus had a last supper with his disciples before dying, quotes his alleged words ("this is my body...blood...do this in memory of me") and then notes that he was betrayed by one of his disciples. Again, no personal revelation involved here - just a historical memory distributed in the early movement that formed part of the verbal tradition that was eventually written down in Mark's gospel.
1 Corinthians 15:3-8 Paul tells us that Jesus had a core of inner disciples called "
the Twelve". Again, no revelation involved here - just an allusion to another verbal tradition.
Romans 1:3 Paul tells us that in "
his earthly life [Jesus] was a descendant of David". That is, he tells us about Jesus's flesh and blood ancestry (this could
only have come from a family tradition i.e. "do you know, our family is supposedly descended from King David").
1 Thessalonians. 2:14–15 Paul tells us that Jewish leaders participated in the killing of Jesus, again that's a reflection of the synoptic tradition of the trial before the Jewish elders.
Then we have quotations of Jesus's teachings in Paul's epistles. In answering the Corinthians' questions about marriage, Paul cites Jesus' ruling on divorce as binding on his followers. "
To the married I say, not I but the Lord, that the wife should not separate from her husband but if she does, let her remain single or else be reconciled to her husband and that the husband should not divorce his wife" (
1 Corinthians vii. 10 f.).
You can find this exact same teaching against divorce in Matthew and Luke - Paul didn't "come up with it" by himself.
Paul tells the Corinthians that "
the Lord [Jesus] commanded that those who proclaim the gospel should get their living by the gospel" (
1 Corinthians ix. 14). This "command" appears in our synoptic tradition in the Matthaean commission to the twelve (Matthew x. 10), "
the labourer deserves his food", and in the Lukan commission to the seventy (Luke x. 7).
As Bart Ehrman notes, "
Paul's first letter (1 Thessalonians) is usually dated to 49 CE; his last (Romans?) to some twelve or thirteen years after that [...] In addition to data about Jesus’s life and death, Paul mentions on several occasions the teachings he delivered. Where did Paul get all this received tradition, from whom, and most important, when? Paul himself gives us some hints. He tells us, he made a trip to Jerusalem, and there he spent fifteen days with Cephas [Peter] and James. Cephas [Peter] was one of Jesus’s twelve disciples, and James was his brother."
