I would almost have to think that TP uses a slightly higher percentage of his brain capacity than a normal person. The things the guy has done and accomplished are far beyond the realms of your typical pro athlete. A lot of times, people that are able to use a higher percentage of their brain capacity end up suffering for it somewhere else whether it be severe social awkwardness or some other deficiency. I remember seeing a story about a young guy that was basically able to draw NYC by memory after one trip over it in a helicopter.
That would be my guess. I doubt it is repressed fear from dirt bike stunts b/c his nightmares would be dirt bike related much how war verteran's nightmares are war related.
We see all the time, Hollywood makes movies about former professional boxers whom had interesting backgrounds, struggles and stuff like that. I think someday down the road a proper film about TP would be pretty badass. Think of a quality movie like "The Fighter" with Mark Wahlberg and Christian Bale but about TP's story.