Hello, I am sorry to hear about your babies ears and know how frustrating it must be. I would suggest at this point to try a different course of treatment with your baby to see if that will help at all.
First I would try and wash or scrub the ears with a shampoo that is specifically made to combat fungal infections on the skin. The best one to try is Ketochlor or one like that. I would then try some witch hazel after you wash it to try and dry out the area. Witch hazel can be found at any human drug store and is usually kept where the alcohol is. I would then try a spray called gentocin and apply that to the ears as well. I would apply the gentocin spray a few times a day and wash the ear tips once a day. I would make sure that you wear some gloves and try to to cross contaminate any areas of the medication or shampoo so not to spread the infection or keep it going on.
If this does not work then you may need to talk to your vet about an oral medication to help combat it so that you are working on it form the inside and outside of your babies body. Hopefully the washing and new medication will help eliminate the problem and there will be no need for the oral medication at this time. I hope this will help your baby but if you need anything else be sure to let me know.