I understand that you are concerned because although your veterinarian said your kitty was fine there are some laboratory values that are outside the "normal" range. It would be helpful to know normals for the laboratory that your veterinarian uses, but I can make some general comments.
I'll address them in order:
Amylase- 1,312 High Amylase in cats comes from many sources, including the pancreas, liver and intestine. The different types of enzymes are called isoenzymes, and the lab test measures the total amount in the blood. It does NOT differentiate between the isoenzymes. Because of that fact alone it is unreliable as a single test result, and we usually ignore these results. Cats with liver, pancreatic or intestinal disease (inflammation) can have high levels. A more specific, much better, test for pancreatitis in cats is a test called a fel spec PL (feline specific pancreatic lipase) as it tells us that the isoenzyme measured is from the pancreas.
Because your fellow has food sensitivities I suspect that his higher than usual amount is due to intestinal sources (inflammation secondary to food sensitivities).
Albumin- 4.5 High This is a blood protein produced by the liver. It can be high due to dehydration, or simply because cats tend to be poor drinkers. This is not really very high, and I suspect it may be a few 10ths of a point above normal, really of no concern.
Osmolality- 287.5 Low This is a measure of dissolved particles (particularly salts, and glucose) in the blood. A higher than usual reading is not uncommon in cats, and likely just says he isn't drinking as much as we would like.
Neutrophil- 78.3 High Neutrophils are a type of white blood cell. They tend to increase in numbers in stressful situations (at the veterinarian, getting blood drawn) and with infections/inflammation. The amount here is likely a percentage based upon the number of total white blood cells counted, which really isn't that helpful. We look at total numbers to see how concerned we need to be. For example if he has 100,000 white blood cells (way too many) & 78.3% were neutrophils that would point toward massive infection/cancer/inflammation and we would be very, very worried. If he has 8,000 white blood cells and 78.3% (6,264) are neutrophils then that is perfectly normal.
Lymphocytes- 15.1 Low This is another type of white blood cell, and it is likely a percentage too, rather than a real number. Lymphocytes tend to be at a lower in percent in stressful situations, if only because neutrophils are released as a stress response. But I would bet total counted cell numbers are normal.
Platelet (Autom)- 54 Low I doubt this is real. Platelets are responsible for forming blood clots and are very sticky cells. They tend to clump together and with a machine (thus noted as automated here) several platelets clumped together are counted as one cell. Generally we have a technician go back and reread the slide manually making sure that there are large clumps of platelets, and thus normal numbers. If his numbers were truly that low we should see bruises and bleeding into urine, stool the chest and abdomen. He would NOT feel fine.
Your kitty's sensitive stomach was be related to food allergies/sensitivities and that may mean he has IBD (inflammatory bowel disease). That will change his appetite. It is best to feed these kitties a hypoallergenic or low irritant food and avoid treats.
If he is losing weight, vomiting frequently or has chronic loose stools then a fel spec pancreatic lipase blood test, and biopsies of his intestinal tract could be helpful in diagnosing his condition and coming up with a treatment plan.