when my son (now 13) would act like a disrespectful hooligan all day during summer vacation, I would send him to work the next day with my DH, a farrier. He loved the time alone with his dad, got an appreciation of where money comes from, and it totally changed his attitude for a long time. (It made him feel like he accomplished something, he got a little money for small tasks, and it wore him out!) My point is, sometimes they need something bigger to focus on, maybe sports or several hrs away from home (not with a bratty friend though!) working towards a goal, ie earning money to buy something big, IDK whatever you think he will focus on? I know baseball is my DSs biggie, my DH talked to the coach about pulling him out for his grades, they went up in a hurry!
btw, weve done the emptying room thing too, it came after several warnings, and it was pretty sobering for him. My son will be so mature and good for awhile then it seems to run out, lol. And he has to hit that boundary AGAIN....seems happier afterwards too! Good luck.