While some of the advice being given may seem contradictory, don't lose sight of the point of it all - consistency.
To get the best out radiotherapy, safely, everything needs to be in the same place inside you, every treatment session. So it's vital to stick to the diet, vital to follow instructions about drinking - to the mL.
Wind is an issue, purely because it won't be persuaded to be in the same place every day.
When in doubt, talk to the radiographers: in my experience, they'll know, but if they don't, they'll soon find you someone who does.
The motto here is "Don't Change Horses Mid Stream"