How many points over a reference range is considered a "mild elevation"? for example, with serum lipase?

Any amount: Reference ranges are set up so that around 3 percent of healthies fall above the top. It's a mild elevation, sure, but no lab value means anything apart from the clinical picture. In pancreatitis, lipase usually runs three times or more the upper limit of reference range. As a tumor marker for acinar cell pancreatic cancer -- if imaging's clear, I wouldn't worry. Best wishes.