Tell him if he really wants away from you that badly, fine. Offer to buy his one-way ticket and passport, just like you buy everything else for him, but tell him once he's off that bus/train/plane he fends for himself. Either he will take you up on the offer, or he'll leave you alone. Either way, you win!

Edit: Read your followup post, and good for you! Keep standing your ground with him. He is a grown man, let him worry about his own mental state, you worry about yours. He will realize soon the hole he has dug for himself.

Do you have anyone you could stay with until you're able to house sit? Any friends or family?