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 are numerous hints dropped throughout the movie that he needs to die to fulfill his role in life, and the directing and storytelling is tight enough that it’s all intentional. Specifically the Confederacy of Dunces references, the phone call asking if the main character in Mile’s novel kills himself, and the “ascension” in the final scene where he is walking up a very sunlit staircase surrounded by flowers.
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.