Hi,

an ACF in 1 gal of water?! That´s way too small, even for an ADF! It´s simply impossible to provide good environmental conditions in that little volume. Toxic nitrogen compounds like ammonia and nitrite build up rapidly (within a few hours), especially when the frog grows. Frogs don´t like salt, it shouldn´t be added on a regular basis. Please read here FrogsArtNeale and fix the environment ASAP, otherwise this frog is doomed. No medication or MarOxy or whatever will safe it unless you change your keeping conditions drastically.
Sorry if this sounds a bit harsh, I surely don´t want to insult you- but it´s necessary to clearly state that deathtraps like one gallon "tanks" are absolutely inappropriate for animal keeping. The fact that this poor frog was able to survive in there for three years only shows how tough they are; it´s not to be misunderstood as a proof that everything is fine.