For those of you who were waiting. Doc says my colon is fine. The 'irregular' thing he biopsied was perfectly normal tissue. Turns out I have an atypical-looking ileocecal valve. Who knew?
So we still don't know where my hemoglobin is going or why my total iron bindability (?) is up. But at least I don't seem to be bleeding from anywhere, nor do I have any scary diseases. Or rather the list of scary diseases I could have has shortened somewhat.