Catch44, there is a lot going on in this thread. My H and I are madhatters, and one of our main issues was sex. I felt just like your wife in our M, so I can relate to at least some things being said here.
Our story went like this:
Over the years of suffering through emotions that I did not understand, I repeatedly sought out IC. My H did not, would not. I tried so hard to understand things while he stayed the same.
After being married a few years, I started to hate having sex with him. I really didn't know why. I codependently blamed myself and tried harder to like it. I never said No.
I felt used and abused since he demanded sex all the time, even after a long day of working and raising young kids. When I tried to share my feelings with close family, they blamed me. They said he was a great guy.
I tried to talk to him, but he was not interested in my feelings. He would pretend to hear me, but nothing ever changed. Then he started to act like I was simply never happy, a nag. He was getting more into porn, paying a lot of money. It went from bad to worse.
Then an old boyfriend contacted me and I had an A. I remember thinking, "Fuck my H. This is no marriage. We will both do whatever the hell we want."
He seemed to become obsessed with sex, addicted even. He is also a heavy drinker, maybe an alcoholic. All the responsibility in the family fell to me, even though we both work. My birthday rolled around and all I got was lingerie.
During my A I felt horrible. I sought out more IC and said, "WTF am I doing? And why?" My IC helped me realize how resentful I was of the lopsided dynamic, the unfulfilling "on demand sex" and I was able to end the distraction A--because that's all it was--and confront my H and my marriage. I eventually told him everything and then said I wanted a divorce. I apologized and said, "This is what I should have done years ago, but I was afraid."
He flipped out about losing the M (not so much the A). He angrily met my requirements for working on the M--committment to long-term IC, reading, and making real changes in his life. As he already knew, I had been reading and working in IC for years. (It took many years to see my codependency clearly and make the necessary changes. Overcoming my own dysfunction has been my greatest challenge and greatest triumph.)
We are years into this now. There are layers, layers that I have still not addressed. Sex remains the biggest, biggest hurdle to fixing the M. I am not sure that I can ever allow myself to be vulnerable to him sexually again.
I live in abstinence. I believe he has stopped seeing prostitutes. (He never admitted it even when I first cut him off and thousands of dollars disappeared from accounts. I know full well that his selfishness continued because he 'deserved it' after what I did, and he was NOT going to live without sex, which is what he initially said.)
My biggest regret? I let the sex on demand, the selfishness, and the exploiting my kindness go on for far too long. I let my resentment build. It was my job to enforce my boundaries, and I did not do my job. The resentment that I felt should never have grown to the size it did to kill the M. I never should have hid from my feelings by having an A. I am deeply ashamed. He did not know how I felt because I was not honest, and that was very dysfunctional on my part. He would have gotten into IC sooner if I had stood my ground.
What does this have to do with you?
Sex on demand creates resentment which kills love. So stop it. You will kill what is left of your M, and it's not too late to save your love.
Your W needs to own her own true feelings and boundaries and people pleasing tendencies. She needs to learn to say No in a healthy way. If she has been taken advantage of, then she has to look at why she has allowed that. The cheating was a weak and broken solution that was no solution at all.
When she is living honestly and you are living respectfully, imho, sex can come into your marriage in the right way. Love + Respect + Honesty = True Passion.