Thank you so much to everyone who has replied! I guess the best thing for me to do right now is to calm down and start preparing. I was going to begin with opening a new bank account and starting to keep my money separately. It's long overdue now anyway, it's been so painful to watch my hard-earned money going down the drain (sometimes literally, when I pour the beer away). And thanks to whereisitgoing for the advise to create a list of unacceptable behaviors. I'll definitely do that, hopefully it'll help me realize what he's doing to me.
Somehow I don't worry much about my son's reaction right now. It's funny, but he once asked me why wouldn't I and daddy live in different houses, because all his friends' parents do.. It turns out all his friends have divorced parents! So at least he would probably take it as if it was normal. I worry more about what would happen to him if I stay. Although my husband is mostly verbally abusive, sometimes he may hit. I don't know if it was a consequence, but my son hit me yesterday on the face and busted my lip. He's 6 and has been a very sweet boy, so it was so shocking to me, and I though it could be a follow up to what his dad did to me just a few days ago, when he pushed me into a wall really hard.
It's so weird to see how easily normal people get together and separate, some having multiple divorces under their belts, and I cannot walk away from a miserable alcoholic for almost 10 years!