Paul spoke at length to James and Peter. All gave their lives for their belief. After the crucifixion they could have just let it all go. Do you reject that Paul was executed? Joesephus reports the death by stoning of James 'brother of the one who was called the messiah'
Paul was never there at any point in that last week, so his belief is what he had.
James? It's time for you to tell me exactly who this 'James' was that Paul spoke with.
Cephas? Cephas was extremely upset by Paul and his ideas, and was the only one who wrote about his experiences, none of which included any witness account of the execution or afterwards during the next 36 hours.
Paul was probably executed in Nero's genocide of Christians, so how does that help any discussion about Jesus and Crucifixion?
Josephus reporting the stoning of a person (James) not at the crucifixion can't help you with any details about the crucifixion.