Toredig, I'm glad you're feeling calmer. Finding that you aren't the only parent going through this stuff - and that your child isn't the only young person who is so troubled and difficult - is very reassuring, isn't it?
foxy, I'm glad that withdrawing your son from school has helped. I'm not surprised. I think school is a major problem for lots of young people, and I thought about withdrawing my own DS more than once, but I knew I couldn't stand it - I needed those hours away from him, and the very worst times we had were earlier this year when he stopped attending college at all, and I got no respite. You're a braver woman than me!
mary, how awful for your DS's friend. And how hopeless. It almost seems inevitable that he'll fail. We've got something badly wrong, as a society, somehow, if young people are left so isolated when they so obviously need support.
brighter, you sound like you are exactly where I was between Easter and September. You say "I'm getting to the point where I don't want him in my day to day life any more" - I was like that for 6-9 months. At the beginning of September, when it looked like he wasn't going to go back to college after all - and he'd left it too late, and had no motivation, to do anything else - I realised I was no longer 'getting' to that point but had 'got' there. I realised I absolutely could not face any more, and had just been hanging on in there since term finished in May, with my sights set on 4th September as the day he would at least have something constructive to do. When he said he wasn't going to enrol after all, my resolve hardened, and I set him an ultimatum I knew I meant.
Thank fuck goodness he did enrol. And the buzz it gave him to be accepted on the course he wanted to do, rather than rejected - which was what he expected, and which has been his big fear all through his teenage years - was enough to re-motivate him, and (so far, touch wood) 4 months later he's still engaged and seems now to be just an averagely-tricky boy, rather than a completely off-the-wall disaster zone.
The trouble is, 'giving an ultimatum' isn't a magic wand. He didn't sort himself out because I told him I would throw him out if he didn't. If he hadn't got onto that course, it would all have gone disastrously wrong. I might not have pushed if I hadn't known there was something he could do, if only he'd get his act together... But really, I pushed because I couldn't stand it any more. Like you, brighter, I knew "if I kick(ed) him out he will go and couch surf with dodgy friends who are mostly older and take a lot of hard drugs", but I honestly think I'd finally got to the point where that option was better than him staying, if nothing changed. So really, it wasn't an ultimatum for him, but for me.
Until you get to that desperate point, where kicking them out feels like the only course of action you can bear, then I think your only option is to hang on in there...
And of course, be nice to yourself, detach, protect yourself, find someone to talk to... :)