First of all: There are few if any constants that we can offer you about infidelity. Like… we can give you examples and even odds of something happening, but it’s hard for us to say that because of A then B will definilety 100% happen. It’s more that we can say that because of A then B has 9/10 odds of happening.
But one thing we can tell you is this: Nothing you did or did not do makes her cheat. That is totally 100% on her. Its not that you weren’t attentive, not sexually competent, body-odor… nothing. In normal relationships people discuss fantasies, wants, lacks and issues and try to resolve them. Going outside the marriage for stuff like she goes… that is totally 100% on her, and I can tell you that with 100% certainty.
I also want to share what I see as the two – the only two – realistic outcomes from situations like this: If BOTH of you are 100% committed to it, you can reconcile your marriage. That requires that she totally 100% opens up on what happened and you can verify each and every detail. Do that and do the hard work and in 2 years you will most likely be at a place where you are either content with having staid, or content with divorce.
Or… If ONE of you isn’t ready to commit to R then divorce. Research shows that as a rule then people that divorce are happy at the two year mark too.
Having said that…
I am honestly not too optimistic for the future of this relationship.
Let’s even write off the incident early on as maybe some unclear boundaries and relationship status. But I would guess your reaction to that would make your expectations moving forwards clear.
The Big Red Flag in the 2020 issue is the knowledge that she needs to keep this discreet. Discreet from whom? Coworkers? His wife? YOU? You aren’t too clear on what made it suspicious, but generally coworkers of the opposite sex tend to keep topics on some non-sexual, non-erotic level, and don’t see a direct need to keep it hidden from their spouses.
What isn’t a flag, but more of a smoking gun is the calculator app. Often used by kids to hide porn from parents.
That shows a couple of things: For one, the previous incidents make it very clear to her where your sand-in-the-line is. Yet she decides to cross it. Only, she shows the premeditation of installing an app and by her own admission used it for some time AFTER your stance was clear.
Do you feel safe that after 2017 she didn’t install some secret storage app in her next phone? Or her present phone? One tip: most phones allow you to see storage-usage.
Can you see if her access is still active? Can you see if she can log herself in to the account? Is there some talk-history that goes into more detail about how they organize their never-happening hookups?
Then let’s add a couple of bonus issues:
The request for an open marriage.
The lack of intimacy.
Add all this together and I doubt you have the truth…
Keeping in mind that IF you decide to reconcile then the next two years (at least) will be paying therapists, MC’s and such, a definite hold on any major purchase or life altering decision (home-purchase, having kids, moving, career-change…). That’s just to reach a place where you can decide if this is what you really want.
So IMHO your first decision is simply if this is enough. If it’s time to accept that this marriage isn’t working and it’s better to cut your losses and move on.
If you want a chance of R then the first requirement IMHO is that you know WHAT you are recovering from. You would need to give her "permission" to tell you the truth, and then have some way to verify it.
Like… let’s imagine she’s telling the truth. That since 2018 she hasn’t been online or flirting or whatever, and that this was all online. If that were true then MAYBE I can see your marriage have a shot.
But how to confirm the truth? Standard suggestion here would be to ask her if she would take a poly where a key question will be "other than Boptimus have you had sex with another man since 01/01/18?"