Hi Ellen,
First of all, my humble opinion is don't give up on the school yet. You mentioned they are still evaluating him for the gifted program. You have an outside psychologist's recommendation.
Does his teacher seem to think he would benefit from the program?
If so, that teacher recommendation could go a long way.
Keep working with the school and keep a friendly line of communication open.
I know this is an anxiety provoking situation, however, try not to worry what will happen if he doesn't get into the gifted program. See what happens with the school first.
If you charge right in with swords drawn, they will circle the wagons on you so fast, you'll never have a chance.
You never know, you might be surprised, they may admit him on the psy's rec.
Keep us posted,
Incog