Hmm. Dunno about a general sound-off about woes and triumphs, Guest, but I can understand why you're pissed off.
What I'm gong to say might piss you off even more, but it's from the heart.
The good news is that, however crappy things seem at the moment, things do get better.
My own son was just like yours - maybe worse, as after he walked out of school, college and home, his primary source of income came from selling dope and piratted software. He had a year or so living on the edge - sometimes rolling in money, sometimes crapping himself in fear at the knock on the door, and then he straightened out.
Eighteen months on, he's earning more than me, holding down a job, living in a nice house and generally showing himself to be an all-round, decent, lovable human being.
All of which he was when he was spending most of his time stoned; just that it was hard to tell through the permanently dopey outlook on life, the paranoia and the anger.
To be honest, you should maybe worry more if your son was a boozer than a spliff-head. My boy had a terrible problem with booze for a while, and managed to get himself into some grim scrapes (including a couple of arrests). Then he switched to dope and - aside from being a zombie half the time - he stopped getting into trouble.
What the lad needs (and I know it's difficult when you feel like grabbing him warmly by the throat and shaking the crap out of him) is old-fashioned love.
It sounds like he might have a problem with self-esteem - it's common with addictive personalities (and cannabis/marijuana can be psychologically addictive for some personalities, whatever it's advocates say. I should know, having smoked it myself for the best part of a quarter of a century!).
Imagine the effect on his self esteem if his old man/step-father tells him he's a useless piece of crap? Love doesn't have to be slushy and wishy-washy - it can be tough. You have to tell him that you don't like his habits, but that you're concerned for him; that you want him to feel happy in his life, and that if he uses dope and booze and booze as crutches he'll never have the strength to find that happiness and self-esteem.
I know things look crappy, but don't give up on him. Neither of you may realise it, but he needs you, and needs your approval. The drugs are an escape from reality. Why is his reality so crappy? What can you do to change it? Both of you face a tough time ahead. Do it together, otherwise only one of you will make it to the winning tape.