J.R.
I was in a similar situation, and I made the tough decision to move on. My daughters were 6 and 3 at the time, and I hated to rock their little worlds, but I knew I was doing the right thing for all of us.
It has been 3 years, and I've neer regretted my decision. My ex has continued to choose alcohol over everything else, so my girls haven't heard from him in 2 years...nor has his family or friends. While that's unfortunate, it's far better than letting his alcoholism affect us on a daily basis.
The bonus: I'm now engaged to the most wonderful guy ever. He's a great father to my girls (as well as his own children). We share the same values, interests and dreams, and I'm happier than I ever imagined. Most importantly, my girls are happy, and they're growing up in a loving, supportive, respectful environment.
Stay strong.