Other than a separation... another possible idea.
If he's not hearing it from you... could he hear it if someone ELSE held up the mirror? Could you ask another poly friend if they are willing to intervene?
And say "Dude, I've noticed you being odd. That's why I stop asking you to social things -- you are hard to be around and you are getting kinda out there. How can we help you let go of this anger that is eating you up?"
But if he's hell bent on self-destructive paths and your own environmental wellness stinks as a result -- move. And try to help him from there. But at least you don't have to be living in UGH all the time. You get breaks.