Stef, adding my welcome. You've come to the right place for help and camaraderie, and you're now a part of our family!
Your story is similar to my own and I'm sure with your great attitude you'll get through treatment with flying colors. I too was diagnosed with a branchial cleft cyst. The first time they did a FNA it came up benign; it was only after removal that it tested positive for SCC.
The notion of a PEG isn't a bad one. I found it incredibly difficult to swallow even water after a couple of weeks of rads. I got to the end, but on reflection wish I'd had one put in. That is, my RO told me the treatment was tough either way but that I could get through it without. And I did. But it wasn't easy.
I also found that the radiation did me in for work. Luckily as a freelance writer I could just take a break. After a few weeks I found I didn't have the energy to sit up for more than 10 minutes at a time, and it took a few months afterward for me to regain my normal energy levels.
Please ask any and all questions here - it's a good bet that someone will have gone through it and offer useful suggestions.
Courage!