[souffle]

Stick with the less sweet veggies (carrots are quite sweet) we give them things like brocolli, cauliflower, spinach, cabbage, kale, cooked pasta, cooked rice are all ok. As a treat ours LOVE the millet sprays you get for birds. Give about a third of one and they enjoy stripping off the seeds.
Sand baths we use a ceramic lasagne dish and baked childrens play sand in ours. Dwarf hams enjoy those more than Syrians actually. They will bar chew often because cage is too small. You sound like you are doing your best for them.
Often changes will make them fight more if you were still keeping them together so watch for that. Place the food in separate areas and bury some so the bully can't be in every area at once and the small one gets a chance to eat.