I'm so sorry you're going through this...(I was with my ex for 2 1/2 years). It sounds like you have your eyes wide open which is a very good thing. It certainly doesn't help the hurt but it will hopefully keep you from delving into the spiral of co-dependency. You're dong the right thing by keeping your distance and now would be a good time to take assessmen of your life and start living it for you and you alone.
Who knows, in time your bf may in fact stick to the program - am I to assume that's what he means when he says he wants to be alone - to concentrate on getting clean? But you can't live holding your breath waiting. I did and another year and a half went by that was much much worse than the first roller coaster ride.
Good luck to you and I hope you stick around.