Well I'm kinda like your boyfriend (except the sexdrive thing, I have a mad sexdrive - only doesnt work when my gf put on too much weight or something), and about the expressing your feeling stuff, let me tell you: I think you'd have to live with it. Even if guys like us try to express them, we feel very uncomfortable with it. It's just the way those people are, but you can usually guess the emotions quite accurately if you know the person and his habits/behaviour.
You can try to find out why he's smoking so much weed. Really excessive drug use that has actual lasting effects on your mood is often just a mask for something. Maybe he had a problem all his life and found this helps him dull it. I know that well.
For the sex thing, you can always try the nonverbal proactive way - get on him, initiate, dont ask or tell anything, just get him going and be really horny. As if you are just gonna use him for sex. This works on me everytime I'm not in the mood, maybe he likes it too.