He smokes and drinks because he likes to be high and drunk. You both can blame it on "stress" but the truth (unfortunately) is that he is either immature enough to check out with various drugs OR his only coping mechanisms are horribly destructive. Neither one of those is a good thing at all.
I am very sorry to say but it sounds like you and your child might be better off without him until he straightens up (if).
Good luck ma'am