You can keep alot in that tank.
I would personaly get about 3 pairs, so total would be 6 fish.
And set up a breeding "spots" for each of the pairs. For example, one on the far left corner, one dead in the middle, and the last one far right corner.
Then, they would end up leaving eachother alone cause they are too busy to defend their territory to even swim to the other ones by accident.
And get a school of small rainbows like madagascar or neon blues to fill up the mid and top part of the tank. Also great fish to distract the dwarfs from eachother and keep the agression level down.
I personaly would get a pair of highfin rams, gold/double red apistos, and kribs.