The thing I couldn't quite put my finger on... Mo... yes, I agree with you... him being married to another or him having sex with another, neither one would necessarily be worse than the other. Especially if you told him to go do it.
Were either of these things to happen in some sort of deceptive way, I'd say you may not be hurt so much by him having sex with someone else, or marrying someone else... but you may very well have issue over the deception/lying itself. ???
If that is the case... I understand and still think it is wonderful that you are in a place where neither thought particularly bothers you. It's very 'un-fused.'
It's the loss of the loyalty/trust of a marriage, that to me, hurt so much. And TO ME that meant more than the marriage OR the sex itself. And that is completely independent of how I feel about myself. I would feel, again, the same way if something were to happen to my best friend... and I am neither married to her, nor do I have sex with her.
The break-down of all of it began with loss of respect... first for myself, and then for him.
Mo, I see you as having REGAINED your self-respect, self-love (not that it was completely gone, if you know what I mean)... but in this state... your H has the freedom to be himself because you no longer need him to be a certain way toward you in order to feel a certain way about yourself.
I think I threw in an additional meaning to marriage that you weren't even discussing.