HUH???

there were several parts of the movie that boggled me. when he goes back in time through his memories or what not, what happens to the current world he's at before going back? does it disappear? or is it like a parallel universe?(many many parallels)
and ya, why did he draw that picture in the beginning? and why was he holding the butcher knife?
one part i really didnt understand was....
why did his father try to kill him? was it to stop the effect he's "cursed" with?
and when he goes back to see his father through a blackout, how does that change the world? Amy Smart becomes a hooker for no reason. someone please explain