The usual worry about the knowns and unknowns, perfectly natural and was the same for me.
The food choice in the Hotel is great - as is the quality. I didn't hear of one issue last year and you'd have to be very unlucky. "Don't eat anything that's been washed, don't eat anything that hasn't been washed" - you would starve.
I'm 92kgs and went with 11% body fat - i've never met anyone who sweats like me but 2 tabs for every bottle of water is what they recommend and was fine for me - i wouldn't go mad, maybe just pop an extra one if it's over 50!!!!!
I took an extreme breakfast, main meal and pudding for each day and a piece of trail food for every 2 hours on the course which was about 15 in total, shot bloks and bars of different kinds. Added to that was a big bag of peanut M & M's and skittles to graze on over several days, a paperami for the stage end and rego powder.
the only other thing was a packet of super noodles for extra before the big stage.
You'll need just as much food for the rest day as every other- you have all day to sit in camp and all there is to do is eat, plus you need to repair after the big one.
If you have a rugby frame - take more and carry it I'd say. Having an extra 800 grams won't slow you down much but running out of food will !!!
Most of the issues I saw were to do with heat exhaustion and pushing too hard, some of the proper runners looked frail before they'd even started!
Enjoy