Tell him no, and that he’ll be coming home to a locked door. If he wants to meet somewhere public, that’s fine. But tell him he’s not staying at your place. Many a 28 year old has been forcibly removed from their parents’ home for much less. Unfortunately, it is his life to live. If he wants to throw it away with those sort of things, then that’s his right. Free will. It’s also your right to protect your health and mental stability. Especially if you’re still looking after your father. You have an obligation to him. If he just doesn’t get it, give him the URL to this page. You put it down in words quite clearly. I wish you the best.