You are so young. I'm so sorry. What made the difference for me, with the same type of MOW, was this:
I took him into his den. I said: "I have taken care of & raised our children (4), house, pets, entertained for you, etc, etc.
You have ONE get out of jail free card. This is it. I don't need you to take care of myself and the kids. So, here is you one chance to come clean about everything. If you can't or won't tell me the complete truth, you can go to her now, because I no longer need you." "There is the door".
" I may cry, be angry, everything, but I will do my best to listen. I also want a time line of every hotel, meeting, (whatever I wanted from him). "
"Make your decision now, or move out tonight". "I deserve better than you."
I was prepared to kick him to the curb, and he knew it. Fog cleared rather quickly. I would have, no question, thrown him out of our home.
Now, he did his best, he told me the truth about some lies, but some came out later. I gave him that, as he was scared shitless. Rightly so.
Bottom line, she's a whore. Will continue to be a whore, and will do what she can to create a wedge. He owes you, not her. Do whatever you can to stay away from her. Yes, its hard, but she didn't betray you, he did. (And yes, I still struggle with this).
We say "Pull up your Bitch Boots and use them on him". It works.
But, you need to mean it and follow through.
(I also opened an account in my name only and had him fund it VERY well, made an attorney appt, which I was able to cancel, and meant business.
Life going well, work in progress. If I had not taken that line, I may have had a fence sitter with a "friend". No F-ing way!