Hi, and welcome. Know how you feel.
When my second husband went back to drinking after almost dying from it, I left and frankly, I am amazed that, fifteen years later, he is still alive. I am not in contact with him, so I can't say how much he may be suffering physically, but he would be suffering even if I were there, going down with him. I can't save him from his suffering, any more than you could if you were to stay.
Just a heads-up, you may want to talk to a lawyer if you haven't already done so. Not all states would allow you to keep the house in lieu of child support even if he were to agree.
Have you been to Al-Anon? If not, I suggest you give it a try.