And this is also based on your H's assessment of his fidelity. A lot of people don't think they are cheating until they actually have intercourse. Even today the idea of an emotional affair is still new. The internet is making this more a known thing. But people over 40 and into 50 still think of an affair as something that happens physically rather than emotionally.
The current research says different.
Your H may have had emotional affairs or flirted a lot over the years but he doesn't think much of it so isn't mentioning it.
Along with puppy's first point. You are basing your info on the testomony of a known liar. He's not in his right head at the moment. He will lie to cover up the mess if he can.
It's clear he's miserable and using her as an escape. That' won't last and you know it.
Just enjoy your life in the meantime and do what you can to keep his family pressuring him. Even if that pressure is to IGNORE his calls and refuse contact with him too make sure they are sticking to that.
The affair will fall apart on its on... Almost all of them do. Particularly if they are under a lot of pressure. That pressure speeds up the end of the affair. Keep it in secret to protect it and it will run for years.