I've been following a lot of your story and it sounds very familiar. It's funny I think I suffer from some of the same issue that you do.
A quick synopsis of my tale (in case you don't want the dirty details). Married 12 years, together fro 18. 2 kids. both under 5.
Last year was h3ll for us. I was a depressed crazy mess and I was certain my wife was cheating in some way. I made her life h3ll with accusations and actions. Finally, I got some help in the form of meds (August) and therapy (Oct). But it was too late. By late August my W started an EA with a co-worker. By early November it was progressing. I found out the dirty details and confronted my wife. she wanted out.
I gave her space and we slept in separate rooms. By late Nov. she took divorce off the table. By Dec we were in MC and we had fits and starts until late March. Our MC "fired" us and things looked good. But life got in the way again and my old issue resurface. frankly, my W is tired.
the last straw was last Sat. when I saw my W txt OM at 8 am on a Saturday morning. That night, I was trying to sneak a peek at her phone to see what the text was about and she caught me.
the next day big talk and somehow my big mouth progressed us to the point where W wants a trial separation. I shake my head. I mean when we started the convo my W wasn't sure she even wanted that.
Anywho we have talk on tap for tomorrow to sort out some of the details of the separation. Frankly, I am freaked out.
Okay enough about me.
I have some of the same issues as you - trusting my spouse, the anger, not snooping and worried about getting that spark back. I do love my W.
I've been reading 25s advice too. great stuff.
I admire that you told your H that it's stay married or divorce. No time for separation. My W is certain, certain, certain that a temp "healing" separation is the way to go. She calls it our "last ditch" effort. But my W is committed to the marriage (funny committed to the marriage, just not committed to sleeping in the same house). She is hopeful, but acknowledge there are no guarantees.
I want to say what you said, but I fear she'd say okay. Divorce it is. I know we can't let fear run our lives, but it's tough.
Patience is bitter, but its fruit is sweet. --Jean Jacques Rousseau.