Just from your posts along he is not a good husband and hasn’t been for years. Damn if he’s not a nice person, he is not your friend, he’s really not a nice person or father.
I would just state- I want a divorce. Therapy isn’t working but your gaslighting did - it doesn’t any more. I know you have are / have had sex with other women - you need to leave now and then we can have an amicable divorce. Right now. I don’t want to discuss it or work on it. I would say it low and quietly. If you have got a supportive family - I would get the children out to a friend and then have a family member there solely for support but actually agree with them before hand just to not say anything and back you 100%, if you think he will kick off.
If you think he will storm off good or that he will go - I’d do it alone and make sure children are out.
if he denies it, blusters or anything. No - you are liar and a cheat.
and then repeat. I wouldn’t discuss what I had found or anything. Let him ponder that- it will drive him bonkers.
I found years ago from my ex husband a bill for a mobile phone in the burn pile in the log burner. It wasn’t for my number or my husbands but was in his name. He had his own bank account. I took at picture.
3 days later whilst he was working in his study with my phone on charge next to him so it couldn’t be me as I only had a mobile, I had a friend ring it from a withheld number (her phone) I went to her house to make the call. He answered - it was 100% him. I didn’t say a word. Put the phone down.
I sat on it for 2 months.
A few months later (6 months plus later) separation and divorce filed (other reasons) I remember him saying ‘ring me later’ and me replying on which phone shall I ring you. He blustered and ducked and dived and said
I only have one phone - he was white as a sheet.
I said - no you don’t. You have more than one and you’ve had it for a long time (!) and you thought I didn’t know, bless you.
He then got angry and denied it. And wouldn’t let it drop.
Then he admitted it and wanted to know how I knew and would not let it drop.
Still over 12 years later he doesn’t know how I knew.
You can keep your own counsel.
Honestly just don’t engage. It took me nearly 40 years to realise if someone is abusive, a narcissist or a cheat and lies - you can not negotiate with them, you can not believe them, your relationship is over and dead. Totally dead in the water.