First of all, the whole point of the butterfly effect in nature is that a very small thing can create a massive change as things progress. In this movie, everything that he does to try to change things is something massive, it is never small. Even when he tries to prove his gift to his cellmate. He slams his hands down on the two paper spikes? Why not just give himself a bad papercut or something.

And I never got a good sense of what he was going to back to change, he never had a real gameplan, it all seemed like he made it up as he went. If he knows the consequences of his actions by having already gone back to change things, then why wouldn't he begin to plan ahead, to try to find an easy and non-disruptive way to undo stuff? It seemed like the film was being tragic just to be tragic, with nothing really driving it other than stupidity.

And the whole idea that his father, and potentially grandfather, had the same illness...what does that add to his story other than some idea of fate, which according to this movie, is bullshit, because you can change your destiny at will.

His prison mate was a Jesus freak and he told him that Jesus talked to him in his dreams. He wanted to proove to him that he had great powers. The two spikes in his hands were supposed to resemble the two nails in JC's hands when he was crucified.