One distubing aspect

Someone using filmmaking to attack someone they resent? No... NEVER!

Yes, I felt that, too.

And I felt that there was a certain amount of deliberate provocation when she was at Marc's house and he flipped out. The camera keeps "peeking" at Marc, when it's clear that he's leaving the situation.

If anyone has dealt with an explosive personality like Marc's you know that it's better to let that person cool off, and not keep poking at them. But I felt that Kim was trying to get a bigger, more dramatic reaction.

I do not feel she resented Marc but do agree he was exploited. Even Kim exploited herself to a degree as well. In the art of the documentary cinema some exploitation will take place.
The one part I had a problem with was the Christmas Eve meltdown and the arrival of the cop: He was obviously told he would be on camera. No police officer is going to walk in on a domestic disturbance and not address a film crew that is in the the thick of it. He would have asked to turn the camera off. It is troubling they obviously briefed him to an extent before he enters the home. Like reality TV shows he simply walks in on camera as if it wasn't there. This is acting to a small extent. His face is shown meaning he signed a release. I hope this was done after the filming and not while Marc was putting himself and his families life at risk.
It's all fun and games 'till somebody gets hurt!

"Considering Kimberly's choice of career, the irony of Marc descending from one of the greatest filmmakers of all time seemed like just one more thing for Kimberly to resent Marc over."

In all fairness, there was plenty that Marc resented Kimberly for as well. He resented Kimberly (as Paul) for being the sports jock and excelling in all the sports that Paul played. He tried justifying this on Christmas Eve by saying he was the school hottie (or something to that effect) and that he "had" all the right girls. He also complained about his own failure of pre-school and having been held back a year and by that time he and Paul (Kimberly) were in the same grade. I think he resented Paul for that even though it wasn't Paul's fault for his own failure. To me, Marc came across as the type who liked to play the blame game and wouldn't always own up to his own failures.

This film was definately a textbook case of sibling rivalry to the end.

Yes, I kind of had a nagging feeling like this too while watching the film. Kimberly comes across as likable, but it did often seem like Marc and his illness were being exploited to an extent. I mean, I think that it is not bad that his story was told, especially since he has died since the film came out. However, I was wondering if his former brother's extensive (maybe excessive?) reappearance in his life didn't really exacerbate his problems. I really felt sorry for Marc. This invasive film and confrontations over difficult issues in his past maybe just weren't things he could deal with well in his condition.

I could see the resentment of Marc from Kim. I could see the resentment of Kim from Mark. I think there were definitely tones of exploitation. I also think that Kim, and the rest of her family all had their issues. During Christmas Marc briefly brings up Christianity and is quickly stifled as though it was a topic the family chose not to mention either for the film, or for Kim's sake. I didn't see this film, though, for it's exploitation. I saw the flaws in every person involved, and it didn't matter to me who was the director, and who was the antagonist or the victim. To me it was kind of a tragic story altogether, and a story worth telling. Even if she didn't mean for it to be presented as it was..