We've been best friends for over a decade, and have roomed together with great synergy for many years. Lately though, he's changed, and has gone full-retard introvert/paranoid/depressed/asshole on me. He hates his job in middle management, but is stuck there (family business loyalty; pays too well to justify ever leaving), and I think this might be contributing to what I'm just going to call his 'condition.'
He's always needed his introvert time, but in the past he's balanced it with a healthy amount of social interaction and novel interests here and there. I should also add he has an addictive type of personality for both substances and interests (classic INTJ subject matter bender syndrome). He is familiar with MBTI, or rather, with INTJness, at least on a superficial level, but as is often the case with INTJs he is primarily interested in his own type, and doesn't know much about other types, or other type-functions. Anyway-- the (somewhat) healthy balance he's maintained over the years seems to have steadily eroded since moving out of the city and into the country, to the point where his routine has tread itself too deeply. He seldom goes out, and he seldom has company (by his choice), and instead follows a weekly formula of wake up-- go to job he hates-- come home, play video games for 6-10 hours (I should add it's the same video game, he just plays it over and over and over again, has probably beaten it a billion times at least), then falls asleep on the couch in front of the TV for half the night, before transitioning himself into his bed for the second half, and repeat. His weekends off only slightly varry from that routine (instead of work, he substitutes buying and cooking a bunch of food, and uses the rest of the time for more video games).
I'm used to leaving him alone, because that's what he wants, and that's one of the things I get about INTJs as an INTP-- but lately he has been stopping me as I walk past to bitch about the most inane and trivial things conceivable. Things like taking too many showers to rack up the water bill, letting my girlfriend use a spare key hidden in the garage to let herself in while I'm asleep, being able to hear her voice ever, keeping my own bathroom that he never uses or steps foot in spotlessly clean, making sure to leave the lid of the washing machine open so mold doesn't build up inside, etc.
The last straw was when he told me that he thought my girlfriend was moving in, and she needed to not come over as often. When I asked him why he thought this considering she has her own house, and only visits 2-3 times a week for a few hours, usually when he isn't even here, never spends the night, and that we keep things 100% to my room just to appease his isolationist nature-- he responded that he just hated the sound of her voice, then called her a 'lying cheating whore,' and said that he just didn't trust her for reasons he couldn't articulate (she is an ENFJ, so technically he was right on all points, but none of it has anything to do with him). Understandable, but for some reason it felt like he was saying he didn't trust ME (since the girlfriend is my proxy and responsibility, and that IMO trusting her is not something he needs to do or not do at all).
Up until that point I was fine taking the high road and being accommodating to his needs, but now I feel like I need to do something else. I feel like I should move out, but I also feel like if I do that he will just spiral farther downward and end up dead. Also I love the guy when he's what I consider 'himself,' and under normal conditions we're great room mates-- I fix the shit that breaks, and he maintains the Te orderliness. He just hasn't been 'himself' in a long time. I know he doesn't mean to take it out on me, I'm just the only one there.
What can I do to help him pull out of the death spiral?
Should I just move out? Would that be perceived as a symbol of judging/betraying him, ie forfeiting our friendship?