I know you've looked at my sitch. I don't know if it was helpful. This is literally the first post I've made that wasn't about ME. I want to help you not be me.
What I'm going to say may be entirely wrong but here it is. You are exactly where I was at the end of May. You're going through what I've learned is called "hysterical bonding." Some people call it "false reconciliation." Like I said, maybe I'm wrong. I'm just telling you what I went through. It was the best few weeks of my life and I thought we had it made.
My sitch is slightly worse than yours. I'm envious, but that doesn't help. About 2 weeks into our "trial" (separate houses) separation, around the beginning of July, I got really accusatory toward W about whether her A had resumed. I had convinced myself that that was the reason she wanted the S.
I made it become true. She lost her mind, told me "You can't control me!" and within a week she was back with him. Just for the one time, but that was the beginning of the end.
Please, if only to make me happy, do EVERYTHING you can to just let it be. The thought of W with someone else horrifies me, but it's not NEARLY as bad as the thought that she will forever be with anyone except me. Don't be the one to make your fear a reality.
Please, drop the snooping. You're only hurting yourself. Ask me if I'll ever forget the picture in my mind of her car parked next to his at the motel. Ask me if I wish "Share location" was never an option on our phones. Ask me where I'd be right now if I had just swallowed my pride and just let it be. You can't stop her from doing what she wants to do, but you can definitely make it worth her while by pushing. Do whatever it takes -- phone a friend, stick some thumbtacks in a rubber band and put it around your wrist and squeeze really hard when you just want to scream. But don't show her that it bothers you. At least, if your sitch is anything like mine, and if you're anything like me, you may well regret it.
If I had read DR and had been on these forums at the end of June, I might still be exactly where I am. But I wouldn't be blaming myself quite so much. You're here and it's not too late. Muster up every little bit of strength you have in you and remind yourself that SHE is more important than HIM.
Focus on her. If she has/had an A, you can't change it. You'll get over that, believe me. It'll be a lot harder getting over losing her.
H: 35 W: 33 M: 11 T: 13
4/10/18: I discovered A and confronted ("BD1") 6/23/18: I moved out 8/31/18: MC ends ("BD2")