Christin, our situations are vastly different, but with some similar threads. I was in a "committed relationship" with my alcoholic fiancee. Like yours, he promised to quit, to turn around his morally bankrupt life. When the deadline came, he chose the bottle. He was angry and revengeful as a five-year-old would be. Oh, how I wavered on holding the line or caving in! It took a lot of support from my friends to say "NO, I will not tolerate your lies and lifestyle." Still, months later I sometimes waver on my decision, even though he immediately became engaged to anothe woman.
Your children are EVERYTHING. He will try to make you believe it is all about him, but make no mistake, it is ALWAYS ABOUT YOUR CHILDREN. My daughter figured largely into my decision. All I have to do is think of her (and she's 19!) and I know I made the right decision. I couldn't bear to have her see him as my husband with the things he was trying to get away with, to do, the awful drinking, the sickening sexual lifestyle.
Stay STRONG! You are doing the right thing. Believe it or not, I needed YOUR post today because this has been something of a rollercoaster day for me too. Your post reminded me of why I left R, and brought back my strength.