Hi Mark
Sorry you are in discomfort . Coughing can be uncontrollable. I would direct your concern to your oncologist. I've had 3 feeding tubes over 3 1/2 years currently without. They were life saving at times when I too could not eat or hydrate orally. It's important you keep up your strength as you still have some way to go.
For me having a g-tube not only made it easier to stay ahead of the curve but also lessened the stress on my caregivers when I was too weak to use the tube myself. At least they could ensure I was being hydrated and nourished when too weak to do it myself.
It's another tool in the box if needed.
Stay positive. It's a tough regime but you will get through it. Take whatever assistance available to you for pain management and nourishing yourself. I've found communicating with my medical team crucial in seeing me through many difficulties and these forums are great for tips and moral support as well..
All the best !
Jack
PS: I've had 89 radiations, 2 neck dissections, 9 rounds cisplatin and currently on Nivolumab (14 months) it's all challenging no matter what stage but you'll get through each one like a champ. Be positive and put your "best foot forward"