I am sure others wil post here as well, but first take a look at this years evaluation of the top 50 cancer centers in the US on the OCF resources page, about 1/3 the way down, a link that says "Best Hospitals" It is a very independent review of who is out there and how they rank.
Also, please ask your doctors for a full body PET/CT fusion scan now to make sure that this cancer has not left the local/regional area of the head and neck. I do not wish to alarm you, but clearly the lymph system is a pathway to the rest of the body. The earlier you know what's what the better.
While this is not important to you right now, I am curious what kinds of scans were done at the end of the original treatment, and what kinds of scans have been part of his annual follow up, and if a neck dissection was offered to you at the end of his treament?
Obviously we are all concerned for you. I wish you the best as you gather more information and move towards dealing with this.