Yes, it's the script. So predictable.
Ok, so things were bad, DS is a handful...and? I assume your vows didn't say 'in times of difficulty you have my permission to fuck all others'? Why does he think he gets to opt out of family life when there are problems!
You have an email address for her. You know her name. She's in your field. I'm betting she works with him or as a consultant etc. It shouldn't be that hard to find her if you really want to, frankly I wouldn't waste my time. She's irrelevant.
It's been going on for as long as he's been acting like someone you don't recognise! A month is all you can prove right now.
'You are not to ruin her life'
...they have done that, not you. If fucking someone else was going to ruin her life, she might should have thought about that before now.
Then there's the issue of him thinking HE gets it tell you what you can and can't do with this bomb she'll, screw that. He's in no position to be 'telling' you what you can't and can't do. Fucking idiot.
I'm betting if she had been prepared to leave her husband he'd have been off like a shot when you told him to leave, I bet he went to her all excited about their shiney new life together and she told him she wouldn't leave her husband...so he came back to you all lovey dovey, albeit wanting compromises! Git.
Of course he put up with so much crap from you, you're the devil incarnate you know
. Tit.
Fuck off waiting until sep 2015. He goes now. You and your solicitor decide what happens about the house.
Maybe talk to the school, see if there are any grants etc available...deferred payments, reduced costs etc. it is shit the kids have to change schools, but they will be fine.
No, no, a thousand times no to the spare room. Don't go there. It doesn't work, it prolongs the agony for everyone.
Phone your PIL tomorrow, tell them that unfortunately die to their sons affair you won't be up to hosting Christmas, but that he might like to go to them as clearly he won't be spending it at your home.
Tell your mum it will just be you and the kids there.
Don't argue with him about whether he fucked her or not. Just say to him that you are not stupid, but it's irrelevant, he's checked out of your marriage and you are ending it. No discussion. He doesn't have to agree, he just has to accept it's happening. I suspect it was on the cards from his pov, but on his own timetable, not yours.
Of course you are in a state, it's a living nightmare. However, and you probably won't believe this right now, but in a years time you'll look back and see how much better things are without him in the house. I get DS calms down too.