I agree with your basic philosophy– that no matter what the betrayed spouse did or does, it is still the cheater who is wrong. This is something I say even when the people in question are my parents. This is what I could tell based on what I witnessed, information I gathered from my sister, as well as logical deductions based on events that later happened.
I will say though that the story of my parents’ marriage was really convoluted and my mother definitely victimized my father with her cheating but his response in reaction also victimized her and it was just wrong. So, to add to the pieces of advice that I’d like to give against normal convention:
3) Just let go. In the long run, everyone would be happier. The sooner you realize it, the happier you will be. The only ones unhappy will be ineffectual and overpaid psychologists.
4) If you need to explain it to your kids, be upfront. Don’t rationalize something or editorialize. I know it’s easier said than done but I know it would’ve been so much easier for me growing up grappling with the moral implications of what I’d seen rather than coming to the conclusion any sane adult would’ve come to about my parents’ actions only after being mentally and emotionally tortured by them. Just communicate with them– neither my mom the cheater or my dad the betrayed spouse ever communicated anything so all I had to go on were what I saw and heard and that was the worst because nothing was sanitized.
5) For betrayed spouses with kids, kill off your emotions and pour all your power into your logic cells. Yes, you were wronged but don’t do things that would fuck it up even worse for yourself or for your kids.
So, that’s my story. I’m not really giving all of the details simply because that’s beyond my comfort level but I wanted to share a different perspective with you since I obviously can’t talk from the Cheater or Betrayed Spouse point of view. Thanks for taking the time to read this.