I think that you'll find permission to accept all of that if you look inside yourself. If you give yourself that permission, I suspect that you'll take a step forward in deciding what's true and what's not.
It's so hard to understand and accept betrayal when you're not responsible for it. For BSes who have built the necessary boundaries, IMO it's impossible to imagine not having boundaries, and Shirley Glass said that As happen in good Ms when the WS lacks boundaries.
I suspect that your WS had a limerent experience. Limerence is a compulsion. I'm susceptible. When it hit me, I very much did NOT want to be in love, so the 1st thing I did was invite my limerent object out for coffee in the hope she would turn me off. The opposite occurred, but at least I had started getting to know her and letting her get to know me. We've been married since 1967.
In our 11th year of M, I got limerent again when I was away from home for a 14 week class. That was awful, because we all ate lunch and dinner and partied together. I went home for the weekend 4 weeks into the class and my crush was over the instant I saw my W. (My LO hooked up with an instructor very early in the class, so my crush wasn't going anywhere outside of my head.)
I met a half dozen potential LOs later in life. Therapy taught me by seeing them as potential partners if I weren't already married to my W, and I kept my main boundary strong. (My main boundary is to say or do only things that I say or do with my W beside me.)
Limerence is a very powerful force, but it's not an EA. If it hit your H, I can see him reacting the way you report.
That's a possible explanation. Even if it's true, it's not an excuse. Whether you understand it or not is not important.
What IS important, IMO, is what you and your H do about it. I'd advise your H to get therapy and make one of his goals 'learning to control limerence with boundaries'.
My reco to you is to take the betrayal into account without excuses. Don't minimize. Ask yourself big questions.
Is limerence a valid explanation?
Do you want to spend the rest of your life with your WS if he doesn't learn to contain whatever it was that enabled him to violate boundaries
Will he learn to contain his limerence?
Does he love you?
Is he in love with you?
Another reco: let your answers and your experience determine whether you'll D or R.
*****
The agony you feel goes with love and/or limerence (he might be your LO, too). I think the more one loves, the more betrayal hurts. Feeling the rage, terror, grief, shame, etc. lets it go.
Have faith in yourself to heal. You really can heal yourself. A good therapist can help, but you probably know that already.