You should be proud of your son for being able to set personal boundaries in spite of what he's seen modeled in the home. He is with his father, and that is where he needs to be. He is not obligated in any way what-so-ever to give your ABF another chance. He needs to be in a healthy environment. Growing up in an addicted/alcoholic home leaves permanent scars on a child. If you're not able at this time to be his mother, than please give your son the respect and the space to do what's right for himself.
If you're ready to get help and turn your life around, please find the nearest Al Anon meeting and run, don't walk.