Don't give up!! Parathyroid tumors are very tricky to find/diagnose. You can even have normal blood work come back of Calcium and PTH and STILL have a parathyroid adenoma that is wrecking havok on your body. Would be a good idea to get your calcium checked in your urine as well.
The food allergies could be from chronic pancreatitis which can be caused from the parathyroid tumor... heartburn is also a major symptoms of hyperparathyroidism.