It is unclear how much of his determination to live among the bears resulted from his love of nature or from his need to escape his problems at home.
Your slightly garbled sentence makes it unclear whether or not you are presenting an either/or, but clearly living among the bears fulfiled both needs for Treadwell -- to experience his love of nature and to -- I would not say "escape," but to find a situation where his personal problems would not trouble him. Your summary is a bit confusing since you say Treadwell developed a "brash confidence" around the bears, and then you cite Rogers' views at length to suggest that Treadwell "cautious, even fearful, around bears he didn’t know, but he developed relationships and mutual trust with a few individual bears over the years."

Though the film raises complex questions that do not lend themselves to easy answers, it has nonetheless been seized upon by the corporate media to denounce environmentalists and those who dare to live on the edge of society.
This may have some truth in it but nonetheless is misleading, since, as the film itself makes clear, the denunciations of environmentalists were going on and took in Treadwell well before Herzog's "complex" treatment came along. Herzog cann't be held responsible for any such crude exploitation of the issues; you acknowledge in this very sentence that Herzog's treatment is "complex," not simplistic.

Treadwell has been called a nut, a certified madman, foolish, obsessive, an egomaniac, bipolar, paranoid and schizophrenic. While his on-camera behavior is often bizarre and at times repugnant, we don't know how much this represents who Treadwell really was or even whether Mr. Herzog selected particular footage to produce a desired effect.
Your logic is unclear, your desire to give Treadwell the benefit of the doubt exaggerated. The film provides a complete picture of Treadwell's accomplishments, even if it is ultimately disapproving of his outlook. (You choose to overlook the fact that he took chances he oughtn't have taken, and that he caused not only his own death but that of another person.) "Who Treadwell really was" surely includes the sometimes (but not exclusively) bizarre moments Herzog shows us. If a person freaks out, behaves bizarrely, it doesn't have to have happened every day to be an important characteristic to consider in evaluating them.

Bizarre or not, the fact remains that Timothy did what he said. He lived in open and honest communication with wild animals for thirteen long years,
You buy into Treadwell's anthromorphism here when you speak of "open and honest communication." What that means, I don't know.

Grizzly Man, under Herzog's direction, veers toward the sensational. In one sequence Treadwell demonstrates the emotional maturity of an eleven-year old in an expletive-laden rant against the Park Service, but the sequence has no timeframe and no context.
I repeat: the occurance itself is significant, not how often -- or when -- it happened, though the film in general does provide careful timelines for events. Treadwell's history and the evidence in the footage show that he was unstable -- although nature and the grizzly world provided a wonderful haven for him where he could be high functioning, on his own terms, and do good.

In another scene that can only be described as maudlin, the director listens to the audio tape of the bear attack (pretending to hear it for the first time)
Herzog has said in interviews and it is pretty well known I guess that he doesn't pretend to be neutral; that his documentaries are works of artifice.

Many critics have called Treadwell delusional for thinking he was protecting the bears. Yet perhaps the most telling fact is that during his time in Katmai, no bear was known to have been killed by poachers. In the first year after his death, five bears were poached.
I doubt that this is good evidence of Treadwell's importance. Bears were pretty safe -- that's why people have pointed out that his "protection" of them was unnecessary -- and delusional.