It seems perfectly fine to me, you're on a good way to repair the mistake
However, stop adding salt when the fungus goes away
Goldfish aren't alt water/brackish fish, so they don't need the constant addition of salt. It could hurt them instead when adding it on a bi-weekly basis, since there's only more and more salt accumulating over time.
Also, a part of the problem could be that you changed all the filter media just like that, rather change half at a time, and you don't need to do that very often. I've had my external filter running and I just changed the thin wool pad since it was getting soggy after several month of use. Never changed on the internal one, and I've had that for more than 6 months by now.
Be careful with the ammonia! You may want to add some zeolithe to the filter in case of emergency, but the beneficial bacteria should do the trick! The symptoms your fish are showing don't seem very serious at all, a torn fin usually heals all on it's own in good water, so focus on using gentle medications, such as salt and mela/pimafix so that you won't disturb the beneficial bacteria, and add A LOT of bio-filter booster!!
Good luck, keep us updated!