I'm not a vet here, but could you say something like:
"I tried living apart but it's not working for me. I need to be with my kids more, so I'm moving back into the house."
If she tries to get you to back down just calmly reassert that this is what you are doing so you can spend more time with the kids, and if both of you living in the house or MBR doesn't work for her she is welcome to take over the lease on your apartment.
Good luck with the boundaries!
Me, WW - Upper 30s BD - Apr 1 2016 EA - Apr 7 2016 (discovered; ongoing for months; did not confront right away) Confronted wife about EA - May 17 Wife sent NC email to OM - July 11