Unfortunately, the most hated person on the planet is a step-parent. Having been one for 13 years I can honestly tell you that it's the most unforgiving and hardest job out there. In my case, my daughter was only 9 and her father didn't become a factor until last year, but everything from enrolling her in school to taking her to the doctor was a constant war against society.

You have the unenviable task of trying to live with a teenager whose mother is still in the picture. His hormones are raging causing paranoia and aggression and he's confused and caught in the middle of his parents and you're a good target. You're the symbol of their failed marriage to him.

The best you can try to do is be like an aunt. Basically leave raising him to your husband because anything you do will be perceived negatively. If you step in, you run the risk of alienating not only him, but the biological mother and your husband. Given time, he may start warming up to you and come to you, then you can meet him half way.

Now one thing that jumped out at me was that you said you're starting to become scared of him. If the situation gets dangerous, you need to get out. Again, because of your situation, there's very little you can actually do, but your safety remains paramount.