OK, so we can't determine the salt amount....
If you can't control the salt amount it is best not doing salt treatment. On another topic, a TDS meter is great for monitoring salt dosage between water changes....and monitor water quality.
When you start an antibiotic, you've got to finish it....so although I don't think erythromycin is going to help, you don't want to create mutant bacteria in your water.... Monitor your water quality as you can nuke it with meds, no hope for the fish in bad water quality.
But you mentioned earlier you have seachem kanaplex? Which is also called kanamycin sulfate. It is a better antibiotic. I would not dose straight away. I'd finish off the previous antibiotic, gradually reduce the salt( you may have dosed enough) and then start some serious water changes. 70% every day for at least 3-4 days if not a week. Then see how it goes, and as a last resort dose again seachem kanaplex.
Water changes are a key to keeping the fish alive while sick, helping the immune system. Meds knock out some of the bacteria/parasites to help the immune system deal with a lesser load. You can't sterilize either tank or a fish.