S.,
You are in an interesting situation. I can't say that I don't understand. I grew up in a "blended family" and live one now. I have a "step" brother that was stealing, into drugs and VERY dangerous. My mom and dad would have him arrested put him in hospitals and rehabs till they were BROKE! I watched what that did to them. BUT they stood their ground and by 8 AM on his 18th b-day his things were packed and on the front lawn right along with him. They are still together and he didn't win. Now on a personal note, my husband and I were faced with a similar situation. I had enough of the double standards and my husband not stepping up to be the father he should have been. My son has now gone down a bad path and I still love him. I met them when he was 2 and he is now 17. As I was getting ready to walk out that door I thought about all I was walking away from. My husband I love very much. my new HOME and my life to start all over again.
I looked at my husband as he sat there crying that I would leave over this and told him, HE makes the choice, either he is a father to his son and step up to the plate and be my husband OR we didn't have a life together. If I walked out I wasn't coming back. The idea that you would leave over this 17 yr old who will be old enough to go live in the real world soon, then what come back? If you really wanted to be married you wouldn't be leaving. That may not be true but it's the impression you give. Don't turn your back on him but you also have the power to make his life a little difficult too!!
Does he have a car? Does he pay for his own ins, gas, payments? Does he have more than the needed items for life? My 17 yr old has to pay for her own clothes and her own lunch at school. Yes she has a job to pay for it. my kids don't have the nintendos and the computers in the room or the cell phones or any of those other things UNLESS they follow the RULES! I have gone in and stripped my daughters room for being disrespectful! All she had left was her bed, dresser and clothes. Cut off the money if he steals it from you have him arrested! If he takes your car, report it stolen! If he's out late, change the locks and don't give him a key, tell him the door is locked at ??? time, if you aren't in the house then don't come home. It's called tough love. It's YOUR house! Make that clear to him. And of course you both need to follow thru! Trust me either he will leave on his own or he will straighten up. Teens aren't easy! This kid sounds like he has a lot of issues. If you care about him let him know you love him. IF you never really cared for him FAKE IT! Tell him it's time this household work together! Either he is a team player or he isn't. He get's to choose! But stick to your guns!! I wouldn't move out if you are just waiting for him to move out at 18. That just lets him know he wins!! Remenber, there are kids out there that have far less than he has! And your husband and you have the power to make him appreciate what he really gets from you!