Nowell, there is also a Friends and Family of Substance Abusers section to Sober Recovery, and you might want to copy your post there since you'll get lots of readers who have experience with pot and other drug abuse.
I am so sorry for your situation. It does sound as if he is descending into some kind of addiction or depression. Taking care of yourself is important. Sorry I don't have anything more specific to offer, I'm thinking of you and wishing you well.
ShootingStar1