Detach means your remove a emotional reaction to their reaction. You "leave the battlefield" You do not jump into the pit. It is very hard to do.
As to A. Yes you need to set boundaries that will define and validate you.
"H, I am in favor of us working at us and repairing this R. This cannot be done with OP in mix. Attentions get divided. You have free choice. With each choice is reward and consequence. If you chose to end A, then the reward is the repairing of our M. If you chose not to end affair, the consequence is that I am unable to stay in a non-monogamous relationship."
You did not metnion D or Sep, you stated you cannot stay. That may also mean you may chose to find someone that can appreciate you. Not that you would, but it will come out of their mouth.
F4W
Through honest giving of my love I will recieve 10 fold in return.
Just because a person does not love you in the way you want, does not mean they do not love you!
