I am sorry to hear that Grey is restless, moaning, refusing to eat and uncomfortable.
It sounds like he may be nauseous since he is refusing to eat and moaning.
In some cases where the dog acts very uncomfortable it is possible that the pup is experiencing some reflux or abnormal motility, or painful intestinal spasms that are more than the usual. In severe cases this can be linked to pancreatitis which is a painful inflammation of the pancreas leading to increased enzyme leakage.
Other possible causes of nausea and abdominal pain include a sudden change in diet, or eating things that they should not like too many fatty table scraps or garbage, bones etc. Addison's which is a poorly functioning adrenal gland is another possibility for waxing and waning abdominal discomfort and nausea. Metabolic organ failures (kidney or liver disease), inflammatory bowel disease or even infiltrative cancers are possible causes as well.
Has he eaten anything he should not have recently (toy pieces, bones, garbage)?
Any changes in food or treats?
Tonight to try and get him feeling better you can give him an acid reducers to try and settle his stomach. Either:
1) Pepcid-ac (famotidine) at a dose of one half of a 10mg tablet per 10 to 20 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one quarter of a 20mg tablet per 10 to 20 pounds of body weight every 24 hours.
These will reduce stomach acid and should help settle his stomach, and hopefully get him more comfortable. These can be used long term if necessary as they are very safe.
I'd also pick up his food and water for now. A couple hours after one of the acid reducers you can offer small amounts of water or ice cubes to lick.
No food for 12 hours. Small amounts of water only.
After his food fast then start a bland diet of 1/3 boiled, lean hamburger (or boiled, white, skinless chicken) and 2/3 boiled white rice. Give small meals several times a day. Feed the bland diet for several days, then start mixing in his regular diet or a hypoallergenic food and slowly convert him to the diet.
If his nausea and abdominal pain continues then he may need injectable medication from his veterinarian to get his stomach upset under control.
So watch him for continued symptoms even with the acid reducers, blood in his stool or vomit or a fever (more than 103.5F rectally), a tense painful belly or lack of appetite after his food fast. If any of those occur it is time to seek hands on veterinary care.
It would also be a good idea to have blood tests done as well to make sure there isn't an underlying metabolic problem like early organ failure, pancreatitis or Addison's disease present.
Please let me know if you have any further questions.