My first husband was an alcoholic and very abusive. I was soooooooo in love with him that I married him a second time so I know how you feel.
There's a kind of excitement and thrill in getting this type of guy to love us--my relationship with my ex was very passionate unlike my current marriage to a non-alcoholic. See if you can find the book Women Who Love too Much--it's open your eyes big-time. When I read it years after divorcing my ex, I got physcially ill it hit soooooooo close to home.
Right now you're severely depressed and you're viewing life through a dark prism rather than reality. It's really tough to accept that, but try to tell yourself that your depression is clouding your thinking and once the depression lifts, you'll be able to see the situation more realistically.
Maybe you could write him a letter as an exercise telling him how he hurt you by detailing some of his more outrageous antics. That would help you remember why you left him and bring put things in perspective. It's really tough not to remember all the good times and conveniently forgot how he hurt you.
Hope that helps a bit.