He can't tell me what to do. Now, that could be a normal reaction. The grief and trauma experienced because of a divorce is added to the feeling that someone is taking the place of their parent. If they get close to their stepparent they may feel that they are a traitor to their natural parent. There is an identify problem that takes place, not only for the teenager, but for the whole family.
Stepmothers frequently spend more time in child rearing than a stepfather.
Rearing another woman's child could create resentment. In addition, the stepmother may be a lot younger than the father. And the teenager might resent this fact as well. Well, a stepfather on many occasions moves into the house of this spouse, the teenager's mother. He may be seen as or even feel like an intruder.