Actually all that is required in Virginia is a letter informing dad of the move and a letter informing the court of the move. Then dad has x amount of time to file to fight the move.100 % correct.
"Write a letter," indeed. That's not how you handle a court order.
Since you've already been gone 8 months and you gave proper notification you will have a better chance of staying in AZ, but you will need a consult with a VA lawyer. Where in Virigina are you at?