vet bills for Blister

My sons brought me this male German Shepard they found wandering our neighborhood. He had obviously been severely burned and tortured. We cleaned him up and cared for his wounds as best we could until I could get him to a Vet. The picture is after He was cleaned up by the Vet. The entire back behind his front shoulders is a mass of burns to the meat. Plus several cuts and infections in both rear legs and his belly. the pics after he was shaved are not pleasant. A lady from work saw the pictures and decided to give him a home since I have 5 dogs and not enough to adequately care for him. but his vet bills have gone much higher than expected. I am helping what I can, but she could use some help. The bills are already over $600 and are going higher. In addition to the medications he is on, he needs medicated baths twice a week for the burns, all of his shots and chipped. He needed a name for the Vet and pharmacy, so I named him Blister. It seemed to fit and she is keeping the name.  Blister is expected to make a full physical recovery. but he needs help. The infected swelling is already going down after a week on meds. He has turned out to be a really good companion for her 2 puppies. They like chewing on his tail and he lets them and they follow him everywhere.
 Why someone could do this to him I have no idea. He is turning out to be a really great dog. Very gentle and despite what has been done to him he has not attempted to snap or bite no matter what we do while treating him.
If you can, no matter how little, please help. Blister still needs a lot of care and trips to the vet and money is exhausted.

thank you