Throwaway not because I don't want my partner to find it, but my ExH stalks my main and thinks that he can use my NM against me with custody.

Cliff's notes:
-been casually NM for 5 years (off and on), mostly when we were apart due to our employment
-both have enjoyed solo activities with minimal issues
-covid hit, being apart was scarce, partner expressed that they wished to be NM while we were geographically in the same area
-rules were established, I (39F) had more luck finding partners, he (38M) struggled, and to be honest I struggled with him becoming emotionally attached or they becoming emotionally attached
-he definitely struggled to maintain the number one rule of honesty and not springing rendezvous on me on the fly
-we decided to explore more threesome and group play and had some success, and decided that solo play would again be when we were geographically apart as the world was beginning to open up and work opportunities were going to happen
-he just went home to visit family (I was there for the first week and he was to remain an additional week)
-before I left I opened the conversation with what were his intentions, was he going to be seeing people, having sex with people, on apps etc etc.
-he told me he was too busy to really meet up but he was probably going to reach out and talk to people, and see what happens
-I just asked that he keep me in the loop, I knew it was going to happen
-last night he went radio silent and I knew, I asked multiple times today for him to tell me what happened and he claimed nothing, he went out for drinks with his high school friends, even went so far as to send me a forwarded video of them drinking whiskey
-then today I get a screenshot of someone from Fet who wanted me to define the nature of our relationship because this is what he sent them
-so I logged in and he was not only setting up things while I was still there on vacation he was doing it when I was trying to be honest and set up expectations
-I confronted him and he admitted that he left his friends last night, met someone, messed around yadda yadda
-I told him that I can't be NM with someone who's not honest and that that portion of our relationship is done until he figures out what the fuck he wants out of this
-I honestly think he enjoys the thought of it being cheating?

-we're in couples therapy and his lack of honesty and my lack of ability to trust his commitment to me are definitely topics we discuss

I just don't know where to go from here, I love him a lot, we have a whole life together, and I don't mind the solo play, I just hate the sneaking and feeling like I'm being made a fool.