WEll, since he's gone most of the time, I don't see how he can get enough custody to significantly change child support.
I certainly wouldn't move to OW's city unless there is some reason YOU want to do so. No need to risk running into them at the grocery store, plus uprooting your kids will add to their sense of dislocation.
As for your kids meeting OW's kids - now that your H has moved out and the kids know you are going to get divorced, I wouldn't worry about it too much. Yes, the kids might resent H and/or OW - not your problem! And it might be the dose of reality that it takes for H and OW's Brady Bunch fantasy to implode. (Keep your kids up real late and feed them lots of candy before you send them, lol). I am envisioning a scene from the movie She Devil, where Roseanne Barr burns down her house and then drops her kids off with her ex at his OWs house, thereby throwing a total monkey wrench into their romantic fantasy. All those kids bickering with each other and fighting for attention might pour some cold water on the whole deal.
