As someone who’s lived very similar relationship dynamics (all these questions are as rhetorical as you want them to be):
Are you trying to be right, or are you trying to heal the relationship? There is no both; what’s the primary driver?
Are your open conversations only happening in the prelude to, during, or post argument? If so, they’re not open conversations.
Are you more concerned with what is actually happening, or with the fact that you feel gaslighted (based on your statement of you needing to have irrefutable proof to bring an issue in the open)?
Are you in a relationship with your wife, or are you a detective trying to solve/catch her?
Now, I’m not saying you’re in the wrong. You could literally answer as negatively as possible to all of those and still be a decent person, but it would mean the relationship would need some serious work and your trust is thoroughly broken. The next question, if that’s the case would be, did she break it, or was it already broken? Who do you have to work through the trauma of to fix your trust the most (e.g. maybe she broke some of it, but if the core of the damage is someone else, go after that first)?
If it’s her and I was in your shoes, imho, I’d get therapy for myself, and a separate couple’s therapist if my partner was willing because it’s very hard to heal from trauma while being continuously re-traumatized.
To be clear, there is no scenario where your sleuthing reactions, no matter how justified, works out in the best interest of you both. We come back to question one, slightly reworded, are you trying to prove what you’re experiencing is valid, or are you trying to heal the relationship?