Facial AVM's are rare. Although my son has some vessels that show AVM characteristics in his face, he has not gone through anything like your son has.
When I first started gathering information, I contacted a mother in New Jersey who has a son with a facial AVM. She was/is a wealth of information. I believe her son must be in his early teens at the moment.
Please email me if you'd like to get in contact with her.
jshiggie@gmail.com
Julie