I'm gonna give it one more week to see how he acts before I have a real talk with him.I would ask him to ensure he is not a nutcase.
If he doesn't like these living arrangements, blame your landlord. He didn't even try to introduce you to your potential roommates. Some of this shit so far is not gonna fly with me. I don't mean or want to be a dictator. He pays rent so it's his home as much as it mine. I don't think it's unreasonable to expect a new roommate to get acclimated to how things have worked in the house. If things need to be changed so we're all comfortable, so be it. Nothing wrong with that.
Even though I do enjoy roommates, my goal is to get back having my own place in the next year. But I'm thinking my rule for roommates is similar to dating women. No one younger than my little sister. This dude is years younger than her. I don't like living with a kid but I didn't have much choice in the matter.