This may sound harsh and I do not mean it to be...
You married the woman who cheated with you- how did you expect to trust her? I mean people can be faithful after cheating but their behavior is much different than it was while cheating. Your wife sounds like she is the exact same way. And her treatment of your daughter is a deal breaker. Never would I let anyone come between me and my kids and I certainly would not be ok with spoiling step children and not helping my own the same way. It is never ok to hit someone no matter how contrite they are. If you had hit her and she called the cops do you think she would have been just as understanding?
The thing is, we teach people how to treat us. If we put up with certain behaviors, then the other person knows that they can keep treating you this way and you will take it. There are no consequences for her actions so why would she change? I do not think it matters if she is a narcissist. I feel like people are quick to slap that label on people with undesirable behavior way to often. Some people are just self centered selfish mean people. I do not think labeling her with a mental illness or personality disorder makes a difference- its just not a healthy way of living. Who's name is on the house? How are your assets split up if something were to happen? Do you have a will?