This Montessori school sounds a lot like one of the schools I visited. Within 10 minutes, I wanted to leave the tour since I knew it wasn't going to work for DD. There is an article I read about a gifted boy on the spectrum who went to a Montessori school and if I recall correctly, I believe by the time he graduated Elementary school, he was ready to go to college but not all Montessori schools are created equal. Your son's current school isn't meeting your son's needs and it doesn't sound like they are willing to change their approach to make it an appropriate placement for him.
