You'll be fine if you plan ahead. I just completed my ph.d in theoretical phyiscs and was much like you, wanted to eat 6+ times a day, sleep right and work out.
Food: My office mates used to laugh cos I was eating ALL the time compared to them. the secret here is to prepare your meals well in advance and to make sure you have access to a fridge and microwave at school. There's usually spare rooms floating around in all departments so if they don't already have those facilities then you can pick some up cheap on craiglist. We bought a fridge for $20 and a microwave for $20 and all chipped in a bit. I'd usually cook up 6 or 7 chicken breasts on Sunday night, a huge tub of rice and a huge tub of veggies etc and keep them in my big fridge at home. Then, the next morning I'd transport a days worth of feed into school in some plastive container. I'd also take up my protein/oatmeal shake, fruit and maybe a wheat bread sandwhich. I'd usually have about 3 to 4 meals ready each day for school, and obviously eat breakfast at home in the morning and my cottage cheese at home in the evening. Just plan ahead man.
Gym: As I'm sure you know, a good workout doesn't have to be a long workout. Most schools have a gym on campus. Ours was 2 mins walk from my office, I used to work out 4 to 6 times a week. Never took more than an hour. I'd take in my shorts/ t-shirt/ towel etc into school with all my food in a big bag everyday. I'd always be able to fit in a workout at some point in the day. We also had a hot tub and swimming pool next door to the science building, so after a long day at school (12-16hrs) I'd usually jump in the hot tub for 20 mins late at night (11pm) to wind down. Plan ahead! :)
As for the sleep, they'll be good days, and they'll be bad. If you manage your time well and take on board some of my suggestions you should be able to get everything done effectively. There are 16 free hours in the day man (if you want to sleep for 8 of the 24). If you plan and have a good routine, there is no reason why you can't devote 12 hours a day to physics, and the other 4 hours to working out, getting up, going to bed, eating breakfast etc. Tweak your routine, don't waste time watching movies and drinking, put all your hours to work for you.
:)
