Coming from severe depression and addiction my own self I saw how miserable he was even in his early years. It was always very apparent in his eyes even when his mouth is laughing and singing and his body moving. He was always overcompensating and in interviews he made it clear he didn't want to shut off that part of him in public because then the truth would shine out as to just how unhappy he is.
I can enjoy the roles and talent he had but it was always somewhat uncomfortable to watch him because his eyes looked so sad. He was very good in dramatic roles even though he is more widely known for his comedic skills.
First of all, I'm glad you're still with us. I myself suffer only from severe depression and I know how hard that can be. I can only imagine what someone who suffers from both must be going through. You should give yourself a lot of credit for sticking it out.
Secondly, I find your comments about Williams to be quite perceptive. Yes, I see much of the same undercurrents that you do. As I've always said, behind the gales of laughter there lurks a hurricane of tears. As an additional insight I see a lot of rage coursing beneath his humor. Anger, as you know, is one of the causal factors of depression. Of course, outrage about human cruelty, stupidity and injustice never plays very well with the American public which keeps its collective head shoved up its own ass, so Williams sublimates and amplifies and drives home this message with his wit. In many ways, that makes him a much more effective agent for change and yet another reason why he will be sorely missed.