Oh how I wish I knew the answers to your questions regarding STBX's move. The girls just got back from a two day visit and it doesn't sound like OW was anywhere around. Without knowing anything about the status of their relationship, it certainly seems like he made the choice of his residence with the girls in mind. The apartment is very close to their schools and several parks. It's also not an place that he would have ever chosen for his own sake (because he works odd hours he has lots of sleeping issues and it is in an area where there would be a fair amount of noise and activity during the day). Also - it actually increases the amount of commuting he has to do (unless he is spending work nights with OW - which is certainly possible and will eventually become clear in time)
One last interesting thing occurred - he bent over backwards to arrange it so that I would have to drop off D7 at his new place after soccer practice - it certainly seemed like he wanted me to see where he lived - which is a pretty drastic change from the hiding out he was doing previously.
Just to be clear- I'm not doing cartwheels of joy over here. Even if he and OW are over and done with, I think he's a way off from being fully cooked. And frankly, given the nature of their relationship - I wouldn't be surprised if it ebbs and flows for a while. But overall, I think it's a positive development - if nothing else he seems to have decided to be more present in our lives and it really seems like he has stopped rationalizing how his lifestyle choice of living so far away was affecting the girls.
I'm perfectly content to patiently observe for awhile (and speculate while on these boards )
)