My [25M] boyfriend [29M] keeps relapsing into drugs

And it’s starting to be a dealbreaker for me. We’ve been dating for about 9 months now. He’s an amazing guy and possesses so many good traits, which is why I chose to overlook it for the time being. At the beginning I told him that it bothers me and he would have to wean himself off of cigarettes and alcohol. But he’s honest with me and tells me he smoked after work this one time, or with friends, or when we’re not together. Or that he craves to have his (more than one) martini on the weekend.

He has a drug history of smoking since his late teens, and drinking since his teens. He’s had a past DUI (I’m guessing, for dumb teenage behavior. A history of meth, cocaine, some other hard drugs. When he gets sad, he likes to drink heavily and not experience sad feelings. Is he just wired that way, and am I wasting my time trying to change him?

I consider myself a healthy person. I very rarely drink, never smoked, eat healthy, exercise. He says he wants to quit, and has reduced his alcohol, but with his exercise habits, the scale should be going down for him, not up. So something is not adding up here. We live separately and I can’t account for what he does when we’re not together.

TL;DR: Was hoping that a guy that I started dating to stop drinking and smoking so much. Worried that he won’t change his habits, less so if we decide to move in together.