Fascinating stuff.
I have further queries:
a) So if the Vice President-elect ascends to the presidency, I'm assuming the Vice President will be chosen in the same way Ford was in '74? Is this correct??
It's hard to imagine otherwise.
The President-elect will have never become President, as he will have never been sworn in as President. No assumption can be made that the President shall have been sworn in. There will be other realities, as "winner of the Electoral Vote". The Vice-President Elect will almost certainly become the President-Elect and have a legally-smooth transition to the Presidency.
Now here is a trickier one. The President-elect (Allen) goes into a coma that he can supposedly emerge from. The Vice-President (Baker) becomes the acting President until the President-Elect (Allen) can and is sworn in as President, and (Baker) is sworn in as President should the President-Elect (Allen) die. The President-elect (Allen) may then be assumed to have been President while incapacitated because he had the chance to be sworn in as President. If he gets the chance to swear the oath of office and does not do so (he is convinced that he will die if President), then he (Allen) never is President, and Baker is assumed to be President all along. The word "Acting" becomes moot. The President-elect (Allen) may have a moot Presidency, but if he is never able to swear the Oath of Office, then he is still President in the history books and for official purposes.
So if Allen dies without regaining consciousness or is shown unable to ever swear the Oath of Office, Baker becomes President without qualification and appoints a Vice-President for Congressional approval.