Hey, I've been having the same problem with the fungus not going away. Check my thread titled "white fungus" it should be high up on the recent posts. Anyways, someone suggested slowly increasing the salt and use chlorinated water. That has actually shown some effect. My axolotl had fungus on two different gills, now one of the fungus areas has fallen off and he only has it on one gill now. What I did was just increase the salt by half a tea spoon every bath. I also used chlorinated water for only the salt bath, I put him back in new DEchlorinated fresh water after each chlorinated salt bath. Also I reduced the time I kept him in the salt bath from 15 to 10 minutes. I WOULD NOT cut off a gill, ever. Bring it to a vet if you're on you're very last resort. I'm sure if you cut it off, the fungus would just grow on the wound. Good Luck!
Also, I should note, mine has been in the fridge for over a month. Sometime these things just take more time.