Rob
My personal experience is that PET/CT scans are worthless except for plotting your radiation field. I am clearly biased but with your obvious research skills, you probably have already found the studies and reports on PET/CT scans problems, especially for base of tongue cancer. As for lymph nodes, my MRI reports did identify "necrotic" tissue and the subsequent neck dissection confirmed that impression.
Have you explored a different ND surgeon? My understanding is that it is like prostate surgery, some "great" doctors are quite good at consistently not having nerve and muscle injury that other "good" doctors routinely inflict. I can relate to your concerns as I simply refused a neck dissection the first time around, but caved in when the cancer came back a second time and I was having so much horrific surgery that the neck dissection was minor. Oh, and my doctor did avoid all damage to all the muscles and nerves but she does many many NDs a year. good luck
Charm