Wow, that must be so tough to leave your little sweetie. But consider, you're going to school to make a better life. You're leaving her with family, people you trust and who love her. Maybe you could ask your Aunt to help you out and be a Mommy Advocate and help her understand *why* you have to go for a bit. My sister always tells my nephew when he stays with me, "Mama will always come back." It seems to help him understand she's not mad or punishing him. I make sure that when we draw or make cookies, we always make one for Mom so she stays in a positive light.
On the food front, it's tough when you're on the go! The baked chips are a great idea. Other good things are apple chips, trail mix, dried fruit, and the Campbell's Soup At Hand, altho be careful of the Sodium in the soups.
Most importantly, don't beat yourself up. You're making an investment to be your best. If you aren't at your best you won't be able to be there for your girl the way you'd like, both now and in the future. It's not just about weight and scales and calories, it's about having the energy to play and living long enough to help her plan her wedding. :-)