Donnie Darko

This was a confusing, interesting, bizarre movie. I'm not sure I really understand what happened. After watching the end of the movie, I guess Donnie died when the "artifact" (aka plane fuselage) landed on his bedroom, and everything that happened in the film after that was...time travel? Even though it was confusing, I loved the movie. Parts of it, like the subplot with the girls' dance troupe and the part where Donnie tells his teacher to shove it, were hilarious. The idea of time travel was intriguing, and I liked the social commentary about the teaching methods in Donnie's high school.
I had a few questions about specific parts of the movie. At 1:38:57, for example, when the teacher talks about the phrase "cellar door"--is that really just foreshadowing? If so, that's a little annoying. I didn't like how this movie tried to tie everything into the plot in a meaningful way. Every twist has to have some deep significance.
Also, at 1:43:33--why does the doctor give Donnie placebos? Doesn't he qualify for some real meds? If they are placebos, then what was the point of the emotional scene where the doctor told the parents that she wanted to give Donnie more medication? I also didn't like how she kept trying to figure out if he believed in God. Donnie never once brought up God that I can remember, but his therapist kept trying to pin down his beliefs. Then again, I think she was probably right to tell him he was more agnostic than atheistic.
I completely didn't understand what happened in the scene that started at 1:52:55. What kills Gretchen? Is she shot, stabbed, run over, or all three? For much of the movie, it was so dark that I couldn't really see what was going on.
And my final, most important question is: did Donnie actually die when the fuselage hit his room? Did Frank ever actually exist? Was most of the movie a dream?During the movie, I kept expecting for Donnie to have one of his eyes cut out so that he could become the next Frank.

Although I didn't fully understand "Donnie Darko", I thought it was a moving, funny, and intriguing film and I'm excited to discuss it on Thursday.
--Sarah