@BirdieMK3 you don’t need to justify your relationship to anyone on here. You and your marriage are NOT the reasons for his current behaviour.
FWIW I lived in a very insular marriage. I was the extrovert, he is not, still isn’t. But we were growing our family and happy just to be together with our children. HE had the affair, I did not! So please don’t listen to those claiming your insular marriage is the issue.
A few wise posters have told you that his behaviour is walking all over the boundaries you have laid out. You are trying to make sense of the nonsensical right now. A husband who would have listened and responded to your concerns is blocking you out, refusing to answer your questions and meeting a woman you don’t know.
I know I wouldn’t bother with a drive of 50 miles to meet an old friend from 20 years ago. I genuinely don’t know anyone who would, especially with so many ways of contacting people.
He’s lying, he’s gaslighting, he’s stonewalling and you’re picking up that right now you’re not safe and that is raising your anxiety.
When my husband did this (and fwiw I was at that point a cool wife so his friendships with very beautiful women and even his ex did not trouble me) I recognised it but reacted badly. She was a new ‘friend’, I picked up on my lack of safety very quickly but I thought I could have a reasonable conversation with him about where these ‘secret’ friendships could lead and he would listen and respond. He did not. I was wrong.
By the point she was a secret and exciting and he was prepared to behave differently with her to his normal behaviours he was already hooked.
I wish to this day I’d been harder. Expressed my boundaries more forcefully. Made him realise that it wasn’t ok.
So in many ways I agree with the forceful approach to alert him to the fact you will not tolerate this.
But I also know how hard that is when you treasure your family unit and marriage so very much.
I know this is a horrendous time and I’m so sorry you came on here and have been attacked.
Your marriage is not the problem. Your husband is.