I feel I need to make some comments, here.
Horrorfest, you were wrong. No matter how much he might have called you names or otherwise verbally harassed you, it's no justification for getting violent. But that's not the real issue, here.
As others have already pointed out, your own story has you refusing to do anything around the house unless you're directly compensated. It has you turning to your mother when your problem is with your stepfather, which can only cause friction in their relationship (which you claim to not want to have turn sour because of you).
You complain about him not living up to his word. And yet, he did take you driving, and he *was* offering it with nothing in return. Meanwhile, have you ever offered him any help? Have you ever heard him doing some yard work, or some cleaning around the house, or anything like that, and gone to check if there was anything you could do to help (even if it was just offering to get him a drink)? Based on your story, I get the sense that you didn't - after all, you get nothing from it.
You spent quite a bit of time in your story invoking your "problems". Your "bad sleeping problems" results in you not waking up until early afternoon - so when one of them offers you driving lessons in the morning, you refuse because it doesn't suit you. And then you complain about them not offering driving lessons. As you've said, your stepfather offered to sell the car to you before he sold it to anybody else - you turned him down. Why should he then feel obligated to keep you apprised of his effort to sell the car to other people? It's not like he promised you the car and then went behind your back to sell it to somebody else.
Your acne situation was invoked to justify a "really bad life". I'm sorry, but are you kidding? There are people out there who were constantly bullied, people who were ostracised from even their own family for being gay, people who grow up in families that can't even afford more than one small meal a day, if that. There are people who grew up on the streets, people who grew up with major handicaps, people who grew up without any family at all. Now, I'm not diminishing your depression - that's entirely valid, and I recognise that nobody can challenge you over that... but it was only depression - that is, the rest of your life sounded pretty solid, to me. You don't get to use acne-invoked depression as a justification for the build up resulting in you violently beating up a guy for calling you names.
As such, I have a few suggestions for you:
1. Learn to let out your anger - don't keep it bottled up. If you're upset with your stepfather, approach him and let him know, feeling the anger but remaining calm about it. If he calls out your manhood or otherwise verbally harasses you, simply respond by pointing out the absurdity of making such claims, and then asking why he feels it necessary to demean you. Feel the anger, but don't let it control you.
2. Much more importantly than 1, start to help out more around the house. Don't ask for anything in return - they are already providing you with food and shelter, and probably a lot of other things (you're on here, I'm betting you have pretty much free access to internet, for instance). If one of them is in the middle of doing something that takes some effort, make sure you go and offer your assistance, either in terms of direct help or indirectly through support (like getting drinks, fetching tools, etc). Every once in a while, ask them if there's anything they need done.
After a while, you'll discover that they'll start making offers to help you, too. They'll offer to adjust their schedules to make sure you get a driving lesson in. And they'll actually fulfil their promises in that regard.
3. Start taking more interest in your mother's and stepfather's lives. You complained about not knowing that they were selling the car until they'd already sold it - if you'd taken an interest, you'd probably have learned about the decision around the same time that they offered to sell it to you - heck, they may have even asked if you had any ideas for alternative solutions to the money situation that resulted in them selling the car.
4. Quite simply, "man up". Stop blaming other things for the situation you find yourself in. Neither your mother nor your stepfather have the time to take you for a driving lesson? Well, how much does a professional driving lesson cost in your area? Can you get a part-time job and earn the money necessary to pay for an hour of it every couple of weeks, perhaps?
Being a man has nothing to do with getting physically violent and beating up other people. It has to do with taking responsibility for your own situation, and being respectful and helpful to others (especially family). Being a woman, by the way, is about exactly the same thing. Turning to violence is adolescent and childish - and the fact that you walked away first doesn't diminish that.