I am sure that asking for a complete S (no nesting) will instigate D.
Why do you think that? Finances?
I think you have a lot of really good reasons to say no, nesting isn't working for you. If I were you, I'd say this is no longer working for me. I'm moving back into the house full time. If you need to go, you can go, and we can work out what to do with the children. But I'm not bouncing back and forth simply because you don't want to spend the night in the same house as me.
Honestly? Why should you be twisting yourself in knots because he is in an EA? Why should you sleep away from your house if he's the one with the issue? And protecting the children-- yes, I totally get that-- but this is on HIM. Not on you. He's the one who decided to step outside your M. You didn't make that choice-- he did. You do not need to bend over backwards to clean up his mess for him. He gets to do that himself. And tbh, I think the more he has to see/understand/feel just how much that mess is going to impact his entire life going forward-- because it will-- the more likely it is that he'll start to realize what a big step this is. (this is where my H got stymied, really realizing what the reality would be if we S.) I feel like enabling this cake eating by nesting is just smoothing it out for him so that he thinks it is all going to be this easy and nice, you taking care of the house and the business and the kids, he cruises in when he wants and off when he wants. Be honest-- even now, I bet you are the one handling the majority of the emotional work around the house with the children, etc. Right?
They say this over and over here, and I think there is a lot of truth to it even though my sitch is slightly different. An A (EA, PA, whatever-- your H seems deep in it enough that it probably doesn't really matter much, except if he hasn't actually slept with her, my guess is that he'll feel less guilty coming back to the M than if he has slept with her) needs to run its course. He simply can't *see* you right now because all he can see is the AP and how she makes him feel. Affair fog, limerence, whatever you want to call it-- he is just not in a place to make rational decisions and to alleviate his own guilt he's rewriting history and treating you like crap, probably hoping subconsciously that you'll flip out and he has more justification for walking.
If he's that determined to S, then I say let him go. You can't control that anyway. But you can control where you live, and I say if nesting isn't working for you, don't do it. Simple. Stick to your guns when you talk about it, don't get into how you feel or what you want for the future, none of that. Just-- I'm sorry, this is no longer working for me. I'll do it for another week or two (if you want) and then I'm moving back in full time. We can talk about how to handle the children. Do not get drawn into a fight or a deep R talk-- just stick to your boundary, validate him, and stay firm.
Please feel free to take or leave this advice-- just my thoughts at the end of a long day. I have strong feelings about this one because it hits close to home for me, it was a part of my H's D fantasy and really takes me back to that place. I'm so sorry you're there. I know it $ucks. It will get better, one way or another. (((SAGE)))
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing