You should be fine - tired but fine - with all the layovers where you can get up and walk around.
I always take food along on the plane. My hubby is diabetic and often has to have something to eat. I usually don't get hungry when I fly, but I try to eat something and be sure to drink something so that you don't get dehydrated. Unfortunately, I can't drink too much because I will have to go to the bathroom. That's OK if I am sitting on the aisle, but not good in the middle or window!
Good luck, as someone said, it will be an adventure!