Good news about Ms. Puff!
You have a very large bioload for your aqurium and the sailfin requires atleast 4 feet (or more) of lateral swimming room. I am thinking the water changes alone are what healed the puffer... keep a very, very close eye on water quality and keep the trAtes as close to 10 ppm as possible. Fish can 'live' in higher nitrates but it will really stress their ammune system. A 125 would better suit your fish load for sure.
I don't know about feeding puffers, sorry. Check this thread out regarding raising copepods...
Culturing Live Food