So sorry :\
You deserve better. If he wants a wife that will be okay with him smoking weed, he should go find one. That's not your responsibility to conform to what he wants.
I'm recently married. (almost 6 months) I'm at that age where I look around and most of my friends are getting engaged etc. People for some reason have asked me about relationship advice over and over and I tell them all the same thing. Marrying someone with the expectation that anything will be different about who they are or what they do after the ceremony is just a very very bad idea. If the marijuana is something you can't tolerate, you'd be doing both of you a disservice to go through with the wedding.
He's made it clear that he doesn't intend on stopping for good.