Most family stories are just that. Stories. If involved in clandestine operations during the war, he would have been a commissioned officer, military or naval, assigned to the Office of Strategic Services (OSS). If after the Central Intelligence Agency (CIA) was created in 1947, it's anybody's guess. I can access records for a fee.
The "Chosin Few" are former members of the 1st Marine Division and attached units who are veterans of operations at the Chosin Reservoir in Korea in 1950.