Any of those 4 options would make sense to me.
It's an exhibition of what is so confounding about the evidence in this case. There are no outright smoking guns that indicate his actual background. The most I'm willing to affirmatively say is that he had a history with aviation to some degree or another. I also don't think it's too far of a limb to climb out on to suggest that he may have had pilot training at some point, perhaps even being a pilot himself.
I believe the fact that he called their bluff on them having to wait for IFR Clearance is highly suggestive of some experience as a pilot that extended past WWII. My research indicates that IFR clearances are a post-WWII mechanism. Military pilots during the war didn't have that training and probably didn't even know what it was. That specific phrase "IFR clearance" doesn't show up on Newspapers dot com until 1954 or so. So him calling their bluff on that, if that's indeed what he was doing, illustrates more recent experience with aviation, from mid-1950's forward.