As a mother, there is something about your situation that troubles me. It seems like you are having trouble understanding that your stbx doesn't want her son to be so far away, or that she changed her mind on such a critical decision .
Regardless of what your son says (and I would really question letting him be the decider at this age), I think it's important, if at all possible, for both parents to be physically present in their children's lives. I say this as a 6th grade teacher who has seen many of my students struggle with their parents' divorces and being shuttled to different homes.
I know this is not the prevailing sentiment on this thread but I wanted to offer a different perspective.
I hope you can both work it out in a way that feels ok to all.
