Here is what you have to think about..it is adjustment. What do you have to adjust too, and how will you do it. You seem to be stuck in wanting to turn back the clock and have it the way it was before. You have to first come to terms with the facts of life...you can't have it be the same as it was with your wife before your step daughter came into the picture.
Once you accept that, then you go on to the next step, and that is to understand your wife in a new way and become a new partner to her. When you do that, all of her anger will go away and you will be at peace with her.
So you must understand that you and your wife should be the best parents possible to her daughter...that is join her, be her partner, and don't fight her. she will appreciate that and respect you for being more of a good man with a good set of values, and if you help her you will feel more manly and fatherly yourself.
Talk this over with your therapist and friends.