I have the same son (DS7 with AS) and he has the same issues with transitions but I do not have any helpful suggestions except time and being positive about the move.  My son recently started having problems in school when we announced he would be going to a new school next year.  I did it on purpose to ease the transition, but it seemed to have backfired.  Now I have LONG MONTHS of transition instead of a short transition.  I wish I could help, but I'm having trouble myself and I can just empathize with you 

  Nan