My wife is a direct descendant of Dr. Doolittle and therefor she will not be seeing this post. PERIOD.
Now I will tell you this not to be cold hearted or mean. But if the mama cat abandoned the kitten it is most likely defective and the outward symptoms are what you see. If you do manage to improve its health in the near term it will develop new maladies. Your best option is to take it to the animal control office and if they determine that the kitten has no liabilities it will most likely get adopted. If not, then they will put it down humanely. We have gone through this many, many times. At present we have four adopted cats and as soon as they have been spayed and neutered they go to friends that have barns and animals to be mousers.
Jim