Hi,
I am hesitant to tell anyone what to do; your choice. But if it were me, I would run and never look back. Like hope said above, the whole family has issues; it's no wonder he's a mess. That said, though, just because his family is messed up is not reason enough for you to throw your life away trying to 'help' him.
I'm sure you can do better, and kids don't need to be around addiction. Just ask mine.....
I don't know what 'cheese herion with Benedryl' would do to a person but I bet it's not pretty....