just a thought on sharing info with the other spouse. How about good old mail.
I'm only a couple of pages in, so if you've already told the OBS, I'm sorry for the repetition.
This is what I did. I found the OBS's work address, and sent my letter (marked personal and confidential) to that address so his wife could not intercept it.
I sent a short letter explaining why I was getting in contact (so he had the info to make informed decisions about his life, so he could be tested for STDs), apologizing for being the messenger, and supplying the details and evidence I had.
He did receive it; OW knew I was going to tell him because my husband never went NC with her. She was looking for it, to intercept. If I had sent it to their home, he never would have known.
As it turns out, they didn't end their affair, anyway---many, many months later, when I learned this, I simply forwarded emails to the other BS to let him know it was ongoing.
It's really important that he know what's going on so that he can make well-informed decisions about his life and health.
ETA: His letter to you? It's 100 percent bullshit. He spent the days he was stonewalling thinking up this plot, very likely with OW's help. (You can be sure she knows this version, so that she can "verify" if confronted. This means your husband is now conspiring against you with OW---I mean, more than he was by having the affair in the first place. It's really bad when the BS becomes the common enemy of the WS and OP. Really bad. It helps cement them together even more strongly.)
So if you have not yet told her husband, now would be a really good time--tell him, with strength of conviction. Because you KNOW what the truth is, even if you wish it were not. Include all the evidence you have, include your husband's latest missive--so that he can be prepared for the gaslighting he's about to receive.
You say that maybe there is truth scattered in your husband's story. Of course there is. Good liars are good because they do insert just enough truth to make their outrageous lies credible to the people who love them and very much WANT to believe them.
But on top of the lies, his tone is just absolutely horrendous. He's accusatory, and that actually makes me worry for you a little bit. A man so cold is able to inflict a great deal of harm to protect himself. I'm not referring just to physical harm; my husband never hurt me physically (well, except by STD). He decimated me emotionally. Your husband sounds an awful lot like him, with his accusations, and "just admit its." You have NOTHING to admit to him; you checked his phone because your gut told you to---and it did so for damn good reason.
Don't let your husband's lies and games---the blameshifting and gaslighting---have the effect he desires.
YOU KNOW THE TRUTH.
You know he's lying.
Make your decisions confident of this.
That doesn't mean you have to leave immediately. It does mean you have to think about whether, if he's going to maintain this ludicrous stance and the defensive attitude, you wish to remain in the marriage.
In your shoes, I'd simply reiterate, "I read your letter. We both know you're lying. I expect honesty and fidelity from my partner---and if you're not willing to be honest and to commit to the VERY hard work necessary to repair the damage your infidelity and lies have caused, I will have to evaluate my willingness to remain in our marriage."
And then, I'd pull a HARD 180. And I'd start getting my ducks in a row.
You've shown you're able to do this--but I know how very strong the pull is to believe, to restore the status quo. Please--don't fall victim to this. It's far more comfortable, I know, NOT to rock the boat. But it's much, much more damaging.
Take it from a woman who did it more than once: it just gets worse if you don't deal with it fully, head-on, right out of the gate.
Millions of hugs to you. I am SO sorry you're going through this.
[This message edited by solus sto at 11:39 AM, April 7th (Sunday)]