Sorry for the super late reply, Uni has been restricting my free time lately. Luckily enough, the twisted limb looks pretty normal now. Seems to have healed all on it's own after about a week of being alone in a seperate tank. It's inside my cupboard so It's relatively cool in there and also pretty dark. Not sure if that helped speed up the healing process but definitely seems to have kept his stress levels to a minimum. I think i might leave him in his temporary tank with regular water changes every 3 days, just until I can fatten him up a little bit as I don't want his leg to get mistaken as excess food in the other tank again.
Also mention-worthy, he's noticeably fatter and has been eating about 2-3 earthworms a day, with the occasional meal worm snack. Cutting up earthworms was a great idea, I only had to do it 3 or 4 times and now he can take any worm no matter the size. The white stuff on his leg went away immediately after one salt bath and I gave him another two after that just to be on the safe side.
Only thing now i'm curious about is the frequency Axolotls poop... Not sure how often Axolotls poop and if it's different for different axolotls, but the one with a twisted limb that wasn't eating much but now eats, hasn't pooped since i put him in the sick tank a week ago. My other one poops usually every second day. Is this normal? He pooped like 3-4 times in one day when I fridged him.
Thanks for all the suggestions and help guys, much appreciated.