Grace you mention apathy, but that state that you fear his moving out will be permanent. Those two things do not go together.
I think you need to sort out your feelings and decide what YOU want. It sounds to me like his affairs have always caused you to hold on for dear life. Not a healthy way to be. You have to move on without him. Either he will wake up and try to catch up, or you will leave him behind, stuck in the past.
The danger here is that if you just let him cake eat, stay in limbo, not work on things and essentially change nothing, then he will just be always ripe for another PA.
Good luck, keep us informed.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018