Your dwarf can have the same fruit and vegetables as a Syrian, since he is not prone to diabetes. I would say you can feed fresh vegetables every day and fruit 2-3 times a week, but start a bit slower like a small piece every second day until he gets used to it (about fingernail size. Here a link to the safe food list:
Safe and Unsafe Food and Plants - Hamster Central WIKI
I have hybrid dwarfs at the moment, but they also don't eat the burgess pellets, so I add a bit of pellet food to their diet. I use Supreme Science Selective Hamster and Mr. Johnson's Advance Hamster & Gerbil. My hamster prefer the Supreme Science Selective (it took a couple of tries, but they eat it now), but they are a lot bigger than the Mr Johnsons, so your hamster might find the smaller ones easier to eat. I give them 1-2 of the big ones or 4-6 of the small ones every two days.