A positive ending for Henry would be a total mood killer, for me. He is a submissive coward with a gambling problem who kept his wife miserable for the last ten years of their marriage. Of course we all know that a lot of this was not his fault, as his current self is the product of bad relationships. At the same time, though, he comes across as someone who lacks the guts to make hard, definitive choices, and that for me is bad enough.
This doesn't mean that I'm opposed to a positive Henry ending, or more than one, for that matter. But any route in which this is possible would need to involve Henry (1) becoming decisive in his dealings with people. The second that he finds out that his wife and Mark have been having an affair, he should kick his wife out of their house, file for a divorce, and sever ties with his former friend. I'm not into revenge plots too much, but I'm sure some on here could think of creative ways for the guy to get back at his mother and others, too. (2) He'd need to lose some weight and cultivate a new appearance. I don't think that this is about competing with other men, but more about having some self-respect. (3) And he'd need to overcome his gambling, as it's implied that he lacks control, which leads to more issues.
I guess what I'm getting at is that Henry would need to become someone who takes the reins; a guy who controls how things unravel around him, even if it means upsetting friends or colleagues along the way. A positive ending for Henry without any of these changes would feel unrealistic and undeserved.