Hi Jen,
Believe it or not, I know where you are at. Check my profile to see my background story - similar diagnosis, but T2N1M0 and in the tongue, not throat.
I never had FU-5 (the acronym just begs for another name, doesn't it?), but I had the rest. I managed to avoid a peg by the skin of my...tongue.
BUT...the treatment delivered. I am here, and I am well again. Your partner's time will come, the nightmare will end. Be sure to consult your own therapist(s) often. Make sure they know what's going on, actively seek their support.
The thing that also seems to be missing from your story is cocaine mouthwash. Ask the treating clinicians if it would be suitable. However, it would seem that your partner's pain, (at least at the moment), is worse than mine, because the patch and OxyContin worked pretty well for me.
In relation to your partner's doctors, be calm, methodical and detailed in how you deal with them. Write stuff down if needed. Get second opinions if you want them. Always be polite, but don't take a backward step, and keep persisting until you get the information you want. Yes, it is much easier said than done.
Ask me anything you like, and I'll try to help. I can probably also put you in touch with my wife, who was my carer.
Best wishes,
Mark.