Matt - you really need to find a new band to play with! Unless you're a toker yourself, it must be a drag for you when the rest of the band is getting loaded and acting stupid. These guys do not sound serious, or professional - at all. Those kinds of bands fall apart from their own gravity at some point anyway. Start your band shopping early this year!
Re: The bass player.
If the guy does not respond to a civil request to move his amp somewhere away from you, (if being reasonable doesn't work...) then Id look him dead in his little pink eyes (best done when he's real high) and in a raspy, whispered voice, I'd swear on my mothers grave that I will obliterate his amplifier if he doesn't move it. If nothing else, it -will- get his attention. It may even sober him up! lol
I also kinda like the, Keith Moon idea!
Not worth it damaging your hearing even if it's music you really love. It's a serious health issue for you and the bass player needs to understand that. Try talking/reasoning first. If no response, then go 'Postal' on his a$$!
Bad situation bro. Shop for another band. Save your ears, your sanity and your lungs!
John