I have dealt with pancreatitis dogs for over 20 yrs. I have yet to have a dog get better quick enough that bloods are normal if tested within a day or two of flareup. In other words false negs happen at the very onset of a flareup, not at the middle..as well, each flareup they have is more severe and longer in duration if not caught and treated.. Its not a disease in my experience that self heals.
If pancreatitis foods need to be low fat to get it under control.. Allergies affecting skin will not kill him but pancreatitis could so I would treat that first and worry about the allergies second. In other words don’t feed a high fat food just because its hypoallergenic.
Ibd can also cause the symptoms you are seeing. If it were my dog and my vet threw out those two options I would request treatment with metronidazole and cerenia-this controls the vomiting and diarrhea and is frequently used in both diseases. I would feed a bland diet for a week and then slowly introduce a lower fat food.
