All puffers can be aggressive to their own kind, and you've got to be lucky if you can keep them in a community tank. Myself I have the experience that I had 3 dwarfs in a 15 Gallon but had to put 1 in his own 3 Gallon tank because the other 2 would not get along with him and even after 2 weeks were still chasing him and nipping him. I decided it got too much when he actually got 2 small bite marks on his lip from getting into a tooth lock fight with the other male. So now I've got a 15 Gallon with 2 dwarfs and a 3 Gallon with 1 dwarf, all happy as ever now.
I really can not recommend keeping any other fish in with them at all, though, its up to you. You might be able to pull it off, however, make sure you'll have a proper cycled tank for the other fish, and maybe a puffer if they do not get along.
As you have probably figured out by now by reading the other thread, but hey! A dwarf puffers diet would mainly be bloodworms, live or frozen. A treat of brine shrimp from time to time will be good to keep the variation in their diet. I've heard of puffers getting a treat of daphnia, krill, prawns, mussels etc as well, but mine ignore all but bloodworms.
A requirement will be snails (or shrimp), feeding them once every 2 weeks should be plenty. They'll need this to keep their teeth down. If they dont get anything to 'cut them off' they'll overgrow causing your puffer to not be able to eat, which will more than likely lead to death.