Paul’s letters are a problem for this theory. He was writing within 20 years of Jesus’ death. I don’t think you’ll find any serious historians of antiquity, secular or religious, who question the fact that Jesus was a real person who lived and died in first century Palestine. That won’t stop Bill Maher from agreeing with you, though! haha
The question is whether the gospels contain Jesus’ ipsissima verba (precise words) or ipsissima vox (precise voice). I vote for the latter, broadly defined. You can see this at work in the conversation between Jesus and Nicodemus in John 3. They more than likely would’ve spoken Aramaic to one another, but the dialogue in John’s gospel hinges upon a Greek word, anothen, which can mean “again” or “from above.” Were Jesus and Nicodemus speaking Greek to one another? Possibly, but I trust you see the problem.
On the disciples’ ineptitude, that is a feature, not a bug. In Mark 8 immediately after the feeding of the 4000, Jesus says, “Why are you talking about having no bread? Do you still not see or understand? Are your hearts hardened? Do you have eyes but fail to see, and ears but fail to hear?”
I highlighted the last bit because it is the key phrase you see in the prophets when the people are so far gone that only parable and symbolic action can get through to them. And what happens next?
They came to Bethsaida, and some people brought a blind man and begged Jesus to touch him. He took the blind man by the hand and led him outside the village. When he had spit on the man’s eyes and put his hands on him, Jesus asked, “Do you see anything?” He looked up and said, “I see people; they look like trees walking around.” Once more Jesus put his hands on the man’s eyes. Then his eyes were opened, his sight was restored, and he saw everything clearly.
Did Jesus need two tries? No, but that’s probably why Matthew and Luke leave out this incident. As James Edwards says in his commentary on Mark,
His healing exemplifies the situation of the disciples, who move through the same three stages in Mark, from non-understanding (8:17-21) to misunderstanding (8:29-33) to complete understanding (15:39). The first “healing touch” for them will come on the road to Caesara Phillippi (8:27ff) when Peter declares that Jesus is Messiah. The disciples will no longer be blind, but their vision will remain imperfect and blurred, for they do not understand the meaning of Messiahship. Only at the cross and resurrection will they, like the man at Bethsaida, see “everything clearly” (v. 25).
Immediately after the two-stage healing, Mark transitions to Peter’s confession of Jesus as the Christ. This is the climax of the first half of the Gospel. Prior to that, Jesus crisscrosses the Sea of Galilee without apparent purpose, but afterward he is “on the way” to Jerusalem. In the first half of Mark, Jesus teaches the masses in Galilee, but then he focuses on his disciples on the journey to Jerusalem. Prior to Peter’s confession, Jesus forbids people from announcing his identity and is frequently in combat with demon possession. After 9:29, there are no more commands to silence and no further mention of exorcisms. In the first half the disciples fail to understand Jesus; in the latter half they fail to comprehend a suffering Messiah rather than a royal one.
Both halves of the Gospel also conclude with confessions of Christ. The first is Peter’s; the second is the Roman centurion’s (15:39). As Edwards says in his comments, “Both confessions teach that Jesus’ true identity is revealed only through suffering – and that those who are called to follow Jesus must be prepared to participate in his suffering.”