Doc is right
I spent over a decade as a Parachute Rigger in the Navy, and did my time instructing aircrew folks in P-Cola and Jacksonville.
The BIGGEST hurdle for any of those (gulp) "young" guys is the mental portion of it. I saw more folks fail cuz they were convinced they "couldnt do it" then I did cuz they actually COULDNT do it.....make sense?
He'll be fine.....keep positive, offer him encouragement...(and btw, remedial PT is common, not an exception)
oh! on the car thing! Don't just "dry store" it till January. You can store it sure, but do what has already been suggested....drive it once or twice a week, make sure you hit highway speeds with it, keep it lubed and gassed up, it'll be fine.
(<===he who did numerous deployments)
Best of luck!