Coccidia is almost certainly the cause of these symptoms. My dog had it terribly as a pup and was very very sick for a long time with the same symptoms. The green stool is a bit odd but could be from eating grass (they often do this when feeling unwell) Continue treatment and let him have a quiet space to rest. The feeding is probably the biggest issue. Try to get some mooshy food (your vet will know the kind) and add boiling water to it to make it a warm paste. You can then syringe feed it to the poor thing till he feels upto it himself.. Also make sure to get him tested for worms if he hasn't been already.
