Paul Giamatti goes into Virginia Madsen's apartment at the end of the movie and we don't know what happens next. How is it implied that he kills himself?
There's even a sequel to the novel with the same characters.
I'm calling "shenanigans" on this whole "Miles kills himself" meme.
Yeah, there are references to death and suicide in the movie, like there is in most fiction about depression. But there's nothing explicit about Miles's fate, and the film ends on an upbeat note ("Because you were wearing your seatbelt!" Jack says to Miles). I've watched the movie 20x and the stuff you list is very liberal interpretation of some scant events.