I think you're getting side-tracked with the whole spanking thing. I spank S5 pretty much all day, and I'm his favorite person. He asks about me constantly, wants to know where I am, snuggles me, etc - if I leave W's apartment, he hangs on to my leg and sobs and begs me not to leave.
You need to focus on the kids, and forget XW. When my XW1 started piddling with OM, and he moved in, I decided to ignore them, and I took the kids camping, roller skating, ice skating, etc. You make life a blast for the Ds, and they'll gravitate to you.
