When do you throw in the towel?

I have been married for 15 years and for 15 year without a break I have had a car note. My husband is always getting new cars and driving them to death and then complaining about them and replacing them with yet another car that he drives to death. I have struggled to pay the bills and he knows this but it does not stop him. We already have a strained relationship because he is just a selfish person and he will admit that he is selfish. He is a recovering alcoholic that suffers from depression and anxiety. I know that this is part of the problem. I have put up with his lashing out and ignoring me for years. At first I just thought is was man thing, but now I know it's not.

He does work hard, I will give him that, but because of that he doesn't listen to me. He has always treated me like opinion doesn't really matter.

I want to leave but I have two young children (7 and 4) and no job. I tried to go back to work last year but he didn't help out around the house at all and he didn't really watch the children (you know make sure the three year old doesn't cut her hair while your in the other room talking to a friend). He makes me feel that I should be grateful that I don't have to work, but work was actually a break for me.
I just need some type of advice on what to do. Is this what marriage is. How long do you tolerate disrespect and just sit and hope and pray that things will change. I have either been going along to get along or trying to pray my way through for 14+ years. When is it time to through in the towel?
I forgot to mention that I have MS.