As far as what youve said, she is already in some kind of affair. From how you are describing your life, you are in a "pick me" situation. Youre forced to watch/wait while she "decides" whether to proceed with this A or to "choose" to stay with you.
Worse. According to her, we are "done". Hence I am trying the LRT, however, I am wondering why I bother.
Because she is making these choices based on her feelings.
Have you ever eaten SO MUCH food that you were like "I never need to eat again? Then the next day or two days later, you felt hungry? How about sad? or hot? or tired? or in love?
These are FEELINGS and they change.
Remember when she probably told you how "in love" she was with you? I know my XW expressed those feelings to me. Feelings change. And there are PLENTY of cases where spouses have felt "out of love" and "done" only to change their minds.
But is she going to be interested in a someone waiting/moping around at home or someone that is going out and leading an awesome life? Im guessing it will only be to the latter. How about anyone else that would want to be in a healthy relationship with you in the future? Again.....probably the latter.
This change has to be for you. But if you dont change, then there isnt really a chance at having a good relationship with her again.