My husband can choke on anything- a swallow of water even, and has a severe reaction, gasping for air, like someone who I has had the " wind" knocked out of him. Possible causes?

See a gastroenterolo. He needs to see a gastroenterologist to find the cause it may be an otolaryngology (ENT) problem, but the gastro person will know.
Esophageal stricture. Your husband i think would benefit from having an egd done and if necessary balloon stretching during the procedure.. Thanks.