I am sorry to hear you are worried about Hunter. My name is Rebecca. I am a veterinarian and will do my best to help.
It would help me to know what tests have been done in the extensive bloodwork. Was his thyroid function tested? Hypothyroidism can be seen in this breed. Was he tested for pancreatitis? That could cause his symptoms, and is not always part of some blood panels.
Was an abdominal ultrasound done to look at his liver, spleen, internal lymph nodes? If his blood test did include thyroid and pancreas testing that is the next thing I would do.
Is Hunter neutered? I would check his prostate gland if not.
Is he drinking a normal amount of water, or more than normal? Did the shot for nausea improve his appetite?
Did he have a fever when he was seen at your vet?
Blood tests tell us a lot, but there are many things we can't diagnose with blood tests. It would help me to see what blood tests were done and what tests were not done. If blood tests do not tell us where is problem is, the next step to me is an abdominal ultrasound.
If you look at his gums, are they pink in color?
Any vomiting at all?
Since I can't see or examine him, the more you can tell me the more I can help.