Just need to vent...

I'm not sure if you want any advise since you said you would like to vent but marijuana doesn't exactly constitute as a substance that you can abuse. It's not like you can overdose on it. I know you don't believe in it and that I can understand but that's obviously not how he feels. The occasional drink doesn't make someone an acholic either. Some people just like a buzz to help let go of the stress that comes with every day life. Sure he doesn't need it, and he's not going to withdraw from it but besides maybe getting a ticket for having a small amount of weed on him I wouldn't really worry about it. Im not sure about the book that the other woman suggested but I personally would think that my husbands beliefs are not what I thought they were. I would ask myself if I could accept that and then go from there. I understand worrying for someone but he's also an adult with feelings and may not feel respected when you try to tell him what he should and shouldn't do. I hope this doesn't sound hateful. Just trying to help by giving a different point of view. 

Check this book out and see if anything changes. Written for Christian marriages. It changed my whole marriage in about 3 weeks. 

The best thing you could do is continue to pray. The bible teaches that is the chaste conversation of a wife that draws a husband to God. You can't control your head but you can go to his head ( God ) and stand in agreement for deliverance for him.