--almost immediately makes me think celiac/gluten intolerance, and associated malabsorptions that go with it (often fat, protein, and vitamins/ minerals).

The biopsies at Mayo--did they include one for small intestine villous atrophy? And have you ever had anti-gliadin IgA/IgG, anti-transglutaminase IgA, total IgA, anti-endomyesial blood tests done (a comprehensive celiac panel)?