I certainly would not use a heater. In most cases it is a chiller that is needed.
I will certainly bow to your greater knowledge of the dwarfs since I have never reasearched them thoroughly nor tried to keep them.
I know a lot more about Kudas and Redi since those are the types I have had.
Also while the small tank may be better for the feeding, I would still be concerned about water parameters, particularly with the higher feeding requirements. Obviously it can be done, but it would take quite a bit of maintenance and monitoring.
Probably the best thing would be something similar to my setup where I have a small pony tank plumed intoo the filtration of my much larger reef. This allows the much larger system to remove the decaying food that the ponies do not eat.
If you do get them, you absolutely must post pics.
I have seen these adorable animals at aquariums and they are too cute for words. I hope you have a great time with them if you decide to take the plunge.