Disable wi-fi on your internet modem and use only cable connections to it. Keep it locked in your bedroom with your only connected computer. Take his phone if you bought it, or quit paying the bill for it if you do. He will leave in a month or two (unless your neighbors have wi-fi connections with no password that he can leach off.) His dependence on the internet will drive him elsewhere, if that provides his only meaning in life. Won't solve his problems, but at least it will solve yours, and you won't be enabling him.