I think a lot of these R's are how my H has felt towards me throughout our marriage and vice versa except that the love never went away completely. As in most relationships one person does something that upsets the other and yes it does cause resentment but maybe H or W does something nice and that somehow cancells out the negative.
It is when there is no feeling left and one or other really doesn't care at all the repression stage that as you say it becomes easier to walk away.
My friend left her H of32 yrs with a small bag of clothes after many years of unresolved issues. Her h wanted to do councelling but my friend said it was too late all feelings for him were gone. Unfortunately it turned out later she had gone to be with his best friend and her friends H. She had been listening to her friends anguish at her H withdrawing from her for months suspecting another woman not realising the personshe'd been friends with for 28 yrs WAS the OW. In my book what my F did was ubforgiveable and after 30 yrs we are no longer friends.

I am sorry you feel D is the only option for you I can see exactly your points as regards the R problems within M and have been suffering from them too. I'm hopeful that my H still loves me enough to keep trying and will be encouraging him to talk through his resentments towards me and trying to let go my resentments towards him. I think when both partners realise it is not all one person or the others fault and there are faults on both sides that there is hope. When one is blaming the other while not seeing what they have both contributed to the problems within the M it stands less chance of success.

Why do so many second and even third marriages fail? Probably because people change the person but not the behaviour that caused the breakdown in the first place!!