what is your theory on how this movie works?  

I wondered what he knew as well.

What do you think?

The way i see it is that he willingly faced his death to save the girl (don't really remember her name) becouse if she never would have gotten to know him then she would never have died.

My way to see this is that he is a schizophrenic guy that was traveling through the time but in a dream that he doesn't knew and he started to confuse it with reality and was having a vision, but not so real, but was a vision about the "end of the world" that is a metaphora for the end of his life. Strange, I hope you could understand my answer haha.