Right from the very start, this whole tale seemed to me to be the result of a kid with an over-active imagination who REALLY loved (& still misses...) his dad, but unfortunately either mis-remembered the details of the stories he'd been told, or didn't have the capacity at a young age to determine whether his old man was spinning a yarn or not.
Sadly, as the kid grew up, it became an obsession & no amount of facts, logic or common sense will now change a belief that has been held, literally, for a lifetime.