OK - I was all ready to reply in anger but I've taken a deep breath and have regrouped. I have an absolutely sick feeling in my stomach for your child...but it is your choice to determine the kind of relationship you have with him (and I often say this about my XAH). I can only speak for myself and say that, as the mother of two young boys, it didn't take me long to decide to get my head out of my a$$ and put their health and well-being above that of any addict in my life.
I really appreciate Anvil's response and encourage you to ponder on it. What is going on inside your heart and head that, as a mother, have made you choose the needs of an alcoholic over your own child? When we devalue ourselves to the point where we put our needs below an A's, there is a problem. When we knowingly make decisions that tell our children "you have less value to me than the person who has abused you"...we need to dig WAY down to answer that.
I hope you find some answers for yourself and I hope that your son is going to a place of peace and comfort. He must be a well-balanced and healthy 15-year-old to make a difficult decision that is truly in his best interest. I'm sure you are proud of him.