I'll offer you one alternate perspective. Let's consider that her affair really is over. If her affair really IS over, and worse yet if it was ended by OM and not W, then this is how W is feeling right now:
-- Sad -- Angry -- Abandoned -- Betrayed -- Semi-hopeless
She will go through the stages of grief that a very pleasurable and emotionally intense period of her life has been replaced with marital strife.
That pain and anger needs an outlet, and there you are.
Therefore, you MAY be experiencing "end of affair" backlash. If that's the case, then your best course of action may be to do nothing for about 90 days. After she has gone through the post-affair grief process, she will think differently about her situation than she does now.
If this is truly what's happening, then you want to continue to exhibit your 180's, but to Starsky's point, no "Mr. Nice Guy". You want to appear to have accepted what she's said, and lean into her plans.
The ideal situation is that her affair grief diminishes concurrently with the gravity and finality of the decisions she's making growing in importance.
You want to step back and let her be, plan in the background and without her knowledge to protect yourself by meeting with a lawyer, and do not set yourself up as her adversary *yet* until you see how this is going to unfold. If she wants to work toward separation and divorce? Fine, she can drive the process and you will work with her on it.
If she sees you continuing to try to keep the marriage together, then she has more time to fence-sit and there is no pressure with regard to the choices she is making. Lean into it.
All this assumes her affair is truly over. If you can figure out if it is over or not, and if it is, how it ended, that would be to your advantage. I would not ask her, as you can't trust her, but try to find out how and when.
Acc
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015