ShatteredApart, you can't reconcile with someone who CLEARLY is still involved with his affair partner and doesn't seem to give a fig about your pain or heartache.
The only one doing ANY work is you. He's the one whose supposed to be cleaning up the mess he made and instead, he's walking around STILL calling all the shots, continually lying to you, and looking out only for himself.
I hate to say it, but your husband didn't "screw up" when he called his affair partner (using his phone card) after emailing that phony NC email to his mistress. That was a very calculated move on his part to give her a heads-up and WARN her that he'd sent her an NC email and not to explode when she read it. He no doubt also wanted to beg her forgiveness for having sent it, and to tell her not to believe a single word in it. He likely also told her that YOU forced him to write it so he did it to shut you up, and he'd like her to ignore it and delete it.
His phone call to her was NO "screw up."
This is exactly why I have zero faith in NC letters. Most cheaters just contact their affair partner on the sly and warn them an NC letter is coming and they apologize for it and claim their betrayed spouse made them do it and that they didn't mean ANY of what they said in the letter, and on and on and on. Hell, alot of these cheaters also ask their affair partners to reply back with their own phony message claming they'll "abide" by the NC request. This, of course, is purely designed to fool the BS into thinking that the affair partners have now ceased contact.
Lastly, I'm amazed you're allowing your husband to completely manipulate you into NOT telling the BH about his wife's affair. Obviously, your husband is STILL protecting his mistress (and more than likely still in the affair with her.)
Not telling the BH is just keeping their dirty little affair a secret for them. Not telling the BH will ALSO insure that you don't have the benefit of HIS eyes watching his wife and keeping you informed if he catches them doing anything. So in essence, you're merely enabling them to continue sneaking around right under this guy's nose and will not have an ally.
Keeping quiet about the affair also doesn't allow the BH to make informed decisions about his own marriage and future, as you're able to do. The guy may be a gun enthusiast and has a few pictures of himself hunting (or whatever) on Facebook, but that doesn't make him some kind of psycho killer, for goodness sakes. It seems your HUSBAND was willing to risk getting shot by the BH over and over and over and over so apparently, he must not think the guy is THAT insane if he was willing to risk his life countless times.
You need to re-think telling her husband. Don't fall for their lies anymore and don't keep their dirty secret for them.
I understand that you want to save your marriage, but until he actually starts doing the right thing and stops the lying and cheating, it's going to continue being an uphill struggle.