He needs to be seen by a vet! They can do a skin scraping. Honestly, I don't think this looks like mange..but it is possible that it is. Only a vet could properly tell you. There is no way that anyone can diagnose this on the internet by pictures; but I have had two pups that looked similar to him and ended up to be beautiful yorkies. Neither of them had mange.
One had fungal and bacterial skin infections that probably started with flea dermatitis. His before and after pics are here:
Index of /cody
The other is my foster Sunny D who I have now. He ended up with a diagnosis of Alopecia X (psedo cushings). Here are his before and after pics:
sunnyd-beforeyt.jpg sunnyyt.jpg
My suggesion is to contact United Yorkie Rescue. They have foster homes in Florida and should be able to deal with this pup if they have room for him.