I think leather ear is a fungal infection, if memory serves.
The other suggestions to treat it, if that is the case, may be options for you, but you might try giving him coconut oil, too...there is a recent thread with a lot of info...and some previous threads as well if you search YT. Coconut oil will help him in many ways, whether or not he has leather ear. Besides feeding it to him, you can also rub a teensy bit of coconut oil on the ears...it won't hurt if it gets into the ears, either...it is anti-bacterial, anti-viral, anti-microbial, anti-fungal, etc. and may help if the issue is leather ear from the outside in as well as from the inside out.
Also, vinegar and tea tree oil kill molds...a vinegar wash shouldn't hurt...or a diluted tea tree oil lightly applied.
The missing ear tip may be due to a previous injury...another animal, grooming accident...etc., and I wouldn't expect the ear tip to grow back, but the hair may when he is in better health.
Good luck...he's such a cutie! I am certain he's delighted to be in your loving arms!
