@Dontknowwhattothink2, there’s a huge imbalance of power here.
Your P feels entitled to:
+develop flirtations outside the marriage.
+control the narrative by blocking transparency/deleting.
+dismiss your need to discuss and ask questions by saying ‘it’s getting old, do what you want.’ A remorseful man committed to rebuilding your trust would never say that.
He clearly laps up these illicit ego massages and couldn’t care less about your feelings and boundaries. He says ‘it meant nothing’ and ‘he didn’t see the problem because he was never going to act on any of it, it was just messages.’ I beg to differ — seeking validation via flirty buzzes with this OW and others is acting on it. They are sharing a mutual attraction and frisson.
His refusal to show you the previous messages suggests they were on a sexual level and/or he was complimenting her, perhaps even criticizing you. Whatever was there, OW sees that he is happy to cross lines and disregard you. His sneaky, disrespectful actions have damaged your marriage, and that is very much something.
@Dontknowwhattothink2, his lies [that it was 1-sided] and his stance on his entitlement to invest in their gratifying, fun kicks [which would enrage him if you did such] shed new light on their meet-up in December, which must have been quite a flirt fest. Her confiding in him about her upcoming surgery shows that they are building closeness. There’s no telling when all of this really started, and I highly doubt that he would permanently block this woman he’s known since school.
He needs to understand that you won’t tolerate this betrayal. My H would be staying elsewhere for a while so I could gather my thoughts and reassess our marriage.