Hi and welcome heartbroken.
I'm sorry for your pain but I know you'll find help and understanding here.
I am a good guy - but when I was smoking pot the pot came first - ahead of job, ahead of family, ahead of partner.
Unconditional love cuts both ways,.yeah?
I saw I could be the man I wanted to be or I could smoke, but not both.
Maybe one day your ex will make that same choice I did and quit - but until and unless he actually makes that choice himself, I think you've done the right thing.
D