The level of salt has been consistent. When I say 1-3, I guess I was implying the range of what people typically put in when they have a sick fish.Not brackish at all. They come from African rivers (not estuaries) and lakes. Start reducing the salt gradually. Doing it too quickly will kill your beneficial bacteria. I'm not sure how to tell you how slowly to do this, exactly, since you're not measuring specific gravity or salinity. Someone else will have to help. If you ever use salt again, pleeeeease be careful! Variation like that, from 1 to 3 tablespoons, will definitely kill your cycle and can hurt your fish. You should be using a refractometer or hydrometer to check your salt levels. Did you work up to this level gradually when you first switched from cichlids to puffers?
Since your salt levels have been varying and your tank wasn't really cycled to begin with, I'd suggest checking your water parameters again. What kind of tests are you using - liquid or dip strip?
Also I don't know how it was implied my tank wasn't cycled to begin with. It was. As far as low nitrates, the color "light blue" and the color "light blue-purpley-blueish-sorta-kinda" on the API test kit (drops) is a difficult one to discern, so I guess I'll call it a .1 ppm.