What did he go through?

Yes, you should be angry with him for wasting his life. There is no problem that couldn't have been solved within the year but he opted out and left you and everyone around him to suffer alone. Obviously he was depressed and perhaps his action was completely out of character, but it doesn't lessen your suffering does it. I suspect the drugs put him to sleep and then the carbon monoxide took over. He may well have been unconscious when he was sick reflexively - or perhaps even after death. Once the drugs kicked in he probably didn't know very much about it. I feel for you in your suffering.......and I think the anger's a good sign..