Hi Sue,
First I want to say how sorry I am that you are having to face this horrible treatment again. Your bravery is inspiring. I just wanted to say that 2 times a day treatment is not unusual - although I havent encountered anyone thats had it, it is commonly reported as a method for 1st time radiation in academic journals on head and neck cancer and has a better chance of zapping your cancer.
I have also read a bit about re-irradiation trials. Its evident that some patients suffer with toxicity problems, but quite few don't. You are young and healthy and have a zest for life so there is every reason to suppose that you will do well, therefore as you say doing nothing is not an option. YOU ARE DOING THE RIGHT THING FOR YOU AT THIS POINT IN TIME. I think thats the only way we can look at these situations. I often wonder how I would have felt if my partners treatment hadn't worked and he had spent three months in agony because of chemo and radiation for nothing. The simple answer is he had no choice. He loves his son (from a previous relationship) and me and felt he had to give it a go. There is no point me even thinking about the whatifs.
For now focus on enjoying being with those you love and getting well. (Although I know its probably very difficult) I would try and practice a mantra that there is no point worrying about side effects that may not happen. If they do it may be a long time away and even then you will still have options.
I know this is not directly related to your sitution, but I hveto share - last night I heard about a friend of a friend -a 40year old marathon runner who went to bed a few weeks ago and never woke up. It really made me reassess all the time I spend worrying about my partner when there is nothing I can really do about anything - I should just be enjoying being with him.
Good luck Sue I think you are going to do good.
Warmly,
Cathy