Oh dear, MM. I'm so sorry for you, you haven't done anything to deserve this.
I started reading your thread, waiting for someone to pick up on this from your OP: she goes on about dh being so flirty and how he loves to party.
But no-one did. You do know what "loves to party" usually means in the context of "flirting", don't you?
Of course things have moved on greatly. I'm shocked that your H is trying to turn his appalling behaviour back on you - though not surprised 
When moving from "just friends" to an affair, cheating partners usually start picking faults in their home relationship. This allows them to detach emotionally, and gives them an excuse (in their eyes) for straying. That old chestnut about the main relationship must be faulty or they wouldn't cheat is absolute crap, you know. People cheat because the opportunity's there and they are weak. But the myth gives weight to the cheat's excuse, iyswim.
Please read "Not 'Just Friends' " by Shirley Glass. It explains all this and how to mend things - if you want to. You'll need him to read it as well.
Personally, I wouldn't want him back. I've done far too much forgiving in my time. But I wouldn't dream of telling you what to do ... except this: Don't trust a word that comes out his mouth, and don't have these difficult talks by email! Face to face is the only way for now.
Gather your friends around you (not that one, obv.) Good luck.