Malt loaf is good, also fig rolls, Kendal mint cake for rapid energy (cheaper than gels and I've never heard of it giving anybody digestive upsets), flapjacks, mix of raisins, dried cranberries, sunflower seeds and pumpkin seeds, and pretzels. For training runs in the 25+ mile range, I like to have some proper food such as a cheese sandwich, wrap or pastie.
Possibilities include peroneal tendon problem and fifth metatarsal stress fracture. I'd get it assessed by someone with proper knowledge - your GP (but be warned they are most likely to tell you to rest it for a few weeks and come back if it is still painful) or a good physio.
+1 vote for a small running backpack. I started with a 5 litre pack with a 1 litre bladder and mesh side pockets for gels or whatever. Took me through marathon and 50K training and races, but I moved up to a larger pack for 50-milers.
Advantage of a pack is that you can easily carry e.g. a lightweight jacket, small tin of vaseline, small first aid pack etc. as well as the water and your choice of food. If it fits well it should be very stable and not feel heavy.
Try them on, with some weight in (e.g. a couple of bottles of energy drink), in the shop and if possible running on a treadmill in the shop, to see if you like the fit.