I am Christian btw, but I support bringing historical and documentary rigor to theology. I also haven't actually doubted anything, at least not of Christ. I've just characterized Paul's gospel and mission as coming from a private and separate revelation, unlike the gospels and missions that the original apostles received.
The point that I made based on that is that it is strange that a lot of the theology of Christianity as it develops centuries later is derived more from the exceptional and privately delivered gospel of Paul, rather than from the gospels of the apostles of Jesus when he also held a historical human form.
I think there is also an obvious scholarly reason for this that doesn't even require belief, which is that Paul's writings are the closest documents we have to the time of historical Jesus. However, that also gives reason for us to be cautious in hanging major theological positions on specific sections in Paul that seem absent from or in tension with the synoptic gospels.