Adult relationship advise

Well, you could start by being honest with yourself. You don't have an amazing relationship. You have allowed your wife to make the rules for 16 years, and you have failed as a parent for most of that time. Step or no, you have responsibilities that you have neatly avoided, and now you blame your wife.
Once you've faced the truth, then make a decision: you can continue to be a doormat, or you can put your foot down.
The choice is yours, no one can tell you what to do. For once, you need to take some responsibility.