Can anyone explain this movie?

I want to like this film but it seems to have a whole lotta logical lapses. It's good when a movie has too much on its mind rather than too little, but a number of things don't make sense. (Spoiler warning: don't read this unless you've seen the movie.)
1) In the beginning Cameron wanders onto the set. There are no cameras visible, no one yells cut, Burt doesn't tell him what's going on and then nearly runs him over, though supposedly not on purpose. All that stretches plausibility a bit much.
2) Burt's body is never found, leading you to think that he might still be alive, but nothing comes of it. Was there a plot twist that ended up on the cutting room floor?
3) Cameron drags Nina up to the high balconey over her protests and tries to get her to jump. What does she see in this psycho?
4) Nina is humiliated that her parents see a clip of her in a nude scene. They would have seen the whole movie anyway eventually, so what'd she expect?
5) Nina's character in the WWI movie is a young woman. By the time of Nazi Germany she's an old lady. That's more or less a 20-year span, so she would have just been middle-aged.
6) Why do they need to film the car going off the bridge again when they already have perfectly good footage in the clips they show to the cops?
7) When Cameron is in the sinking car he grabs the air hose under the seat and finds it disconnected, which suggests Eli really is out to kill him. But at the very end we're supposed to believe that all of Cameron's fears about Eli were wrong.
8) Actors playing German soldiers corner Cameron on the river shore, so apparently they changed the ending in which the hero drowns. Yet their decision to change it is never discussed. If the hero lives that would seem to negate the scenes of Nina's character as a heartbroken old lady.
9) Why does the hero in a WWI movie have a bad 1970's haircut?