Don't underestimate the value of a sober and decent ex, particularly if you have kids together! My first husband quit drinking before we got married, but since our divorce, I feel very, very fortunate that I don't have the drama and conflict so many divorced couples have. In fact, we have become better friends now than when we were married.
I don't know why your situation turned out the way it did, but it will be good for you to work past the anger and bitterness and to work on forgiveness. Forgiveness is not, BTW, something we do for the person who wronged us, it is something we do for ourselves. You can have a great life if you can unload the burden of anger you're carrying. It takes time.
Hugs,