There are several (including myself) who have had rx more than once, and I hope they chime in as well. I had radiation twice 2nd time using IMRT tx which is very precise, I don't think there were any crossover areas for me. I know I was never warned about potential consequences the way you have been. Try looking at it this way - there is a 95% chance that you will not have any life threatening side effects, and an 80% chance that you will not have major side effects.
While I believe the 95% figure, I think the odds of serious side effects are more like 50%. I have had continued ongoing fatigue since the 2nd radiation. I deal with it. Some days it is debilitating, some days not. Swallowing continues to get more difficult as time goes on but I have yet to lose any weight - so all good there. Strengthen your throat muscles as much as possible with eating and swallowing exercises. The mucus will probably get worse too - buy a water pik which cleans your mouth out and you feel fresh as new. things like mouth sores will clear up in time - but the odds of you getting mouth sores will always be higher.
So yes, there are many ongoing radiation side effects that you can reasonably expect. But, I am here, and I am prepared to put up with them. These are my "new normal", and I am glad you are looking for a realistic view of the future.
I don't think your physicians would undertake this round of radiation if they believed that the life threatening side effects were any more than 5% so be confident in that.
There are several of us who have had radiation more than once, so I'm sure you will hear from them as well.
Hugs
Donna