What a lot of you describe (symptoms) sounds neurological, for best results, ask your vet to refer you to a veterinary neurologist.
I am assuming the dog has not responded to treatment by your regular vet within a reasonable amount of time. There are effective medications available by prescription that will put a halt to the suffering. The first step would be to get further testing, maybe by a specialist, and hopefully that will result in an accurate diagnosis, from there you can evaluate your treatment options.
Example: Complex Partial Seizures (aka Psychomotor or Behavioral): Seizures: are associated with bizarre or complex behaviors that are repeated during each seizure. People with complex partial seizures experience distortions of thought, perception or emotion (usually fear), sometimes with unusual visual, olfactory, auditory and gustatory sensations. If dogs experience the same things, it may explain the lip-smacking, chewing, fly biting, aggression, vocalization, hysterical running, cowering or hiding in otherwise normal animals. Vomiting, diarrhea, abdominal distress, salivation, blindness, unusual thirst or appetite, and flank biting are other signs. There is an obvious lack of awareness though usually not lack of consciousness. Abnormal behaviors may last minutes or hours and can be followed by a generalized seizure. Complex partial seizures are usually associated with secondary epilepsy. (excerpt from) http://www.canine-epilepsy.com/FAQ.html
