Hi Rachel, sorry you are in this place. I agree with gigi that it's not a good idea to file unless you want him back right now, in the sorry mess that he's in, or, you are prepared to follow through with D if he doesn't come back right now.
You deserve to be respected and valued - he is showing neither of those. He's cake-eating, and hoping (even asking) that you'll wait in the wings in case things go wrong with OW.
DB like mad and go NC as much as you can.
Can I ask why you do want him back, given that this is not the first time it's happened? What qualities does he bring to your M?
Sending hugs!
M:49 H:49 T:20 M:18 D:16 D:14
EA: Feb 2019-May 2020 Separated: Mar-early Aug 2020 H asked to reconcile: Jun 2020 EA relapse: Oct/Nov 2020 Recon #2: since Nov 2020