So many things in here I want to comment on, so little time in which to do it.
Katyg, you I think you should do what is best for you. By all means, give the guy another chance, and give the relationship everything you have. But if that effort isn't being reciprocated, then you really need to ask yourself if it's worth it. You have a life too, and you need to look out for yourself.
I think what your partner said to you was beyond harsh, but we all make horrible mistakes we're all ashamed of.
I'm a reformed pot addict, and
ngdawg makes a good point. Pot really messes with your shit, although giving it up was one of the easiest things I've ever done. If you feel like exerting any control in the relationship, I reckon you should direct it at him not smoking weed on any regular basis.
We can all tell you what to do, and tell you what we'd do, but there's no emotional attachment for us. Only you truly know the situation, and you have to most to loose. Just don't let yourself get fucked around, as others have said, life's too damn short to be miserable.
All the best
