Cheaters exposed - I wrote to her husband

So a few weeks ago I found out my partner had been talking to and texting another married woman- a nurse at the local MIU - so I phoned her and spoke to her and let her know I would tell her husband.. Both he and the woman denied anything physical had actually happened - he deleted her number and promised me he would cut contact … we tried working through things but I’ve been suspicious ever since. So the other night I opened his phone, and there in the call log is the same number without a name saved.. I’d already screenshot it last time so I knew the number… she won’t answer the phone, he’s begging and pleading that I forgive him… We have kids and a home so it’s not as easy as just walking away… I’ve been looking for her husband on social media but can’t find him, So today I wrote a letter and hand delivered it to her house with my insta details so he can contact me if he chooses to… why should she get to sleep in a happy home when she helped destroy mine?? I’ve told him what I did - let them both be accountable.. I thought it would make me feel better but it really hasn’t