Assertive which is firm but reassuring, clear but concise. It's the best way to set boundaries with friends, also give the guy a hug or kiss on the cheek, he earned it with the good book choices.
Nothing, we are the noobs, we need to adjust to our elders. He's creepy more cause we don't understand than anything he's trying to do. If he wants to help us to be less creeped out he can teach us more about himself and his time at crying rock.
Choir, a battle tune can turn the tide. Public speaking, a skilled orator can turn shapeless rage into a weapon of passion. Computers cause Alex can help with our homework!
I say we go all john woo-ey and brawl up his face! Hell with the hole in his gut we can jam our fist up through his chest into his face and work him like a puppet!
Start packing, let's take away some of moms stress. She can handle the landlord if she's already been handling him. If it gets yelly we can step in. Actually let's bust our ass to do as much work as we can. It sounds like our mother has to dramatically change her life because of us. Least we can do.