[quote] "Don't forget to hate your mom for me". [/quote]

I hate my X. I can't stand anything she does. But I would never ever say anything like that in front of my daughter. That is wrong on so many levels. My X told my daughter yesterday to tell her step-mom and step-sister to shut up.
Kids that age are still trying to learn how to deal with there emotions and can pick up on other peoples emotions. If you X is feeling concerned about the move then your son can be picking that up. Especially if his dad is expresing his feelings to your son.