Wow -- does your story sound familiar. My husband and I were in the same position as you guys are. I even found my self either subconsciously or intentionally sabotaging our marriage (picking fights, suggesting he work late, paying bills late) because I thought if we started to hate each other, that would make a divorce less painful.
My husband was an angry (although not violent) drunk. He'd just get more and more agitated until some little thing (like the kitchen trash can needing to go to the garbage bin) would make him explode. Yelling, red and sweaty faced, intimidating me with his size and implications. Finally, I couldn't take it any more -- I was scared our boys would actually see him freak out one of these days (it was ordinarily after they went to bed) or I would kill myself and leave the kids with my parents. One day when AH was out carousing, I called my dad and asked him to come get the kids and I. I took the dog and the boys and went to my parents. My AH moved his stuff out the next day, to go stay in a friends' rental that was currently unoccupied. I stayed with my parents for several days, then went back to my home. During the next few weeks, I only communicated with AH via email, and he only saw the kids via his parents. He ended up getting clean and getting in AA, I got sober as well and we're getting marriage counselling, as well as me getting treatment for what was a 2-year severe depression.
As terrible as it was to leave my home, then come back and see our closet empty of all his things, to put our boys and both of our sets of parents through, I am happy that it happened. It's only been just under 90 days since my husband moved back home, but we've made some very positive changes. No alcohol. Attending church. Seeing the marriage counselor. Things are still a long way from being fixed, but we're making forward progress; the change in our kids is remarkable -- they are so much happier and more relaxed. I very well may have been dead by this time; I couldn't take the pain and misery of being 2 drunks missing our opportunity to be great parents and great people, and I was pretty much ready to end it.
I have great sympathy for your position; you're making the right choice, no matter how absolutely wretched it makes you feel. Make sure to get help with your alcoholism, and maybe see a doc about underlying depression that is quite likely to be present after all these years. If you still love your husband (the one you originally fell in love with, the one you know is under all the alcohol), make sure you find a good marriage counsellor and use it. We had spent so long just knowing we had a perfect marriage, we did absolutely nothing to nurture it; when trying times came to pass, we had no tools whatsoever to work through them in a rational, kind manner. Now, as I mentioned, things are not all peachy. We do actually make each other laugh from time to time, call during the day, go do something and have fun, for the 1st time in ages. We're doing all we can to make a better life for our kids and ourselves.
Have courage and do it for you and for the wife your daughter will one day be.