I'm sorry I haven't had the time to read your whole thread, but I think I have the gist of the grief your xh is throwing your way. First, I don't think you're being defensive in any way, nor overprotective. The things your xh says to your son is pretty nasty and quite honestly I wouldn't want to have your kids spend an extended amount of time with him in CA. OTOH, at least if he were in the same vicinity at the time of the visits, I could understand them being with him. I don't trust the guy's actions especially at such a distance with the kids.
Is there anyway, and forgive me if I've missed this possibly happening in my hasty reading, but is there anyway your kids can speak to the judge about being required to go to CA with your h? There are cases where kids have "ruled" where they go and at 14 and 15 they seem old enough to not be uprooted. Especially with you son and his sports, can't he use that as reasons not to go?
Laughing, I feel for you and all that you've been enduring of late. I wish I had the magic answer, but hopefully your lawyer can figure out the next step.