I quoted that selection because they too had similar conditions.
They were serum normal but still benefited from supplementation of B-12 but I agree with you it is probably not the B-12 or your Homocysteine levels would be elevated too?
The low normal hemoglobin might be a sign.
Here is a study about "Anemia of Aging" that shows low normal Hemoglobin to be key in diagnosing OSA in older individuals entitled "Anemia of aging and obstructive...
You might not be far wrong with the B-12 that and Iron possibly.
Here is some research I came across that might help you.
"A Case of Plummer-Vinson Syndrome Showing Rapid Improvement of Dysphagia and Esophageal Web after Two Weeks of Iron Therapy."
An this research entitled "Dysphagia resolved with vitamin B12 therapy: a case of esophageal parakeratosis"