Is it okay for a married man to go out alone with a female coworker?

Assalamu alaikum, I need some advice. My husband said he was attending a dinner for social networking with his coworkers and listed 5 people who'd be there. At the last minute, everyone else cancelled and it ended up just being him and another sister. She booked their ride, they were together for about an hour and a half-he didn’t message me at all-and then he left when her friend arrived. He met me later for our weekly halaqa. Just to be clear, this wasn’t a mandatory work thing, just a casual gathering. He told me he knew I’d feel uneasy but he went anyway, saying he didn’t want to cancel suddenly. He also didn’t tell me beforehand because he thought it would stress me out. Honestly, I do feel uneasy because of how it appears. I don’t think he should be alone with another woman, and I hold myself to the same standard-I keep my distance from non-mahram men. What bothers me is that he went knowing I’d be uncomfortable. A week ago, something similar happened: he stayed out really late playing board games with colleagues. I told him I wasn’t okay with it, but he stayed until the end. I dropped it then. He’s been seeing a therapist and keeps saying his therapist told him what he did isn’t haram. He repeats that a lot. We already have other problems in our marriage, like lies and trust issues. But even setting those aside, this situation feels off. If you respect your wife, why would you do something you know upsets her? I’m not sure how to handle this.