Hi welcome to SR my daughter is the addict in my life. The way I see it the guy did you a favor by breaking up with you. In my opinion you should just move on with your life. As you know you can't save him. Try to find something that interests you an throw yourself into that for a while. In time you'll get over this guy an find someone new.
Good luck there will be others come along with a lot better advice than I can give. In the mean time read the stickies at the top of the page.