You'll know you are progressing further when you don't need the why. Also, the answer to all of your questions is the same answer-- his natural proclivities plus alcoholism. Alcohol frees it all-- they say and do things that looked at through sobriety and logic are asinine, insane, inane, self-destructive, cruel and moronic, and they do it consistently and repeatedly.
Never, ever, ever, ever try to make sense of the things alcoholics say and do. Each and every one of those things makes absolute sense when an alcoholic without long-term sobriety is involved-- THAT'S WHAT THEY DO AND SAY.
Now, when sober people say and do the same **** then it is completely different. That's when I think they are just stupid, crazy, or both (me included).
Good luck finding your way to not needing to know why. I truly wish you the best.
Cyranoak