I think you need to stay calm and play it cool. If you have the kids, find somewhere to go or something fun to do with them.
Your W is wayward and showing much disrespect for you as her H. You feel she can hold your past mistakes against you. You cannot allow your past mistakes to be her free ticket to cheat with OM. In other words, you repented of your affair.......and she is not excused to pay you back by having her own affairs. She uses your past indesgretion as leverage. I hope you can see that she is not excused. Don't let her play games with your head by making you feel guilt. That is the past. Today she is the one who has wayward behavior.
Do not act as if you are a victim. Don't act as if you are being punished. Hold your head up and walk tall. You are a man, not her little boy. You must respect yourself before she will respect you.
Until her respect for you is restored, I don't think she will get better. She may be nice some days, but don't let it fool you. Niceness does not mean anything has changed under the surface.
You can start by not allowing her to speak to you disrespectfully. She doesn't get to talk down to you, yell, curse, belittle, blame, etc. Don't allow her to show disrespect in front of your children. She doesn't get to boss you. You should not cater to her and treat her as if she royalty. If she speaks with sarcasm, address it at that moment. Don't try to pay her back at a later time, b/c that is passive-aggressive behavior. It never resolves the issues.
She likes to eat cake, but you don't have to serve it. Know what I mean? You are not helpless. Learn to say, "no" to her face. Don't be afraid of her. Stop apologizing for the past.
I think this may be a very long road ahead. Be sure to read the threads about wayward wives.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!