Reading through your list, I realize how deeply I have been influenced by Quine.
I, too, but mostly methodologically.
I learned logic by reading Quine, and have always found his views and thinking to be the most convincing and clearly stated of almost any writer. I too find modal logics essentially meaningless, I don't believe in possibilia (how many possible men are standing in an empty doorway?),
I see you've been influenced both by Quine's good arguments and his bad ones, Pat! :-) The answer to your (and Quine's) question is utterly obvious: None. (You said it was empty, right?) There is of course a perfectly coherent question here: How many men *could* be standing in that doorway, which happens, as a matter of fact, to be empty? Assuming we're talking about possibilities in which our actual physical laws hold and in which humans are more or less as they actually are, the answer is, well, as many as could fit. Two, surely; perhaps up to five or six for particularly short, skinny and acrobatic men. Isn't that obvious as well? And by going to the trouble of measuring the doorway we could say with great precision exactly how many men of such and such dimensions in such and such physically possible positions could occupy the doorway. Things of course become less clear (and perhaps more justifiably subject to Quinean ridicule) if we allow possibilities in which, say, men could be two or three inches tall. But that some philosophers take such possibilities seriously is hardly any reason to cast aspersions upon modality generally. Our ordinary thinking about the world is infused with modality and I daresay we couldn't make it through the day without assuming that a wide variety of modal propositions are true (hence perfectly coherent).