Hold the horses, people - Shredmeister made a comment that seems to be being overlooked:
I keep hearing comments along the line of "He's just a teenager - don't be so rough on him, don't cut him off from his family, etc etc."
The above described behavior is NOT normal teenager behavior. This is the behavior of a very disturbed young man.
In my opinion, he needs psychological help - from a psychiatrist, not simply a "counselor." And until his tendency toward violence is assessed and under control, his interaction with his siblings needs to be very strictly monitored.
He sounds so imbalanced and disturbed that his time with his siblings should probably be limited as well. If the truth be known, they would probably appreciate being shielded a bit from his behavior.
When it comes to violence and threats of violence, breaking the law and endangering others, one must take a very strong stand. The stakes are simply too high to treat the offender with kid gloves and sweetness and light.
I support a zero tolerance level for violence and threats of violence. You should make it clear to your son that you love him - but also make it clear that you will intervene swiftly and thoroughly (in ways that will be unpleasant to him) if he continues to be violent - in words or actions.
I would get law enforcement involved if necessary.
Continual lying is another very destructive trait, and one that is very hard to live with and operate with as a family. Besides being irritating and undermining of trust, it is extremely disrespectful. I would make sure that there are consequences that "fit the crime" when it comes to his lying. If he uses the car and then lies about where he went, I'd take his driving priviledges away. If he stays out past his curfew and then lies about what he was doing, I would ground him. If he lies about doing his homework, I would make him stay in the living room and finish it, and then review it - and I'd call his teachers or whatever (here we can get online to see homework assignments) to check up on his follow thru. You get the picture.
It's very trying. But get this - he's 17, not 14. If he continues to refuse to abide by the household standards and expectations, and make the people who support him tense, frustrated and miserable, I would tell him it's time to move out when he graduates.
As my oldest son loves to say, at that point he will be a grown *** man.