The difference between compelling Disarmed and the one-off tag of Off Balance is that Disarmed A. means the character can't use their higher Weapons/Guns skill to attack, B. Cannot take advantage of the Weapon rating, and C. Has to take specific action to correct this or else he's stuck without it for the scene. The one-off tag of Off Balanced means that the opponent gets a single +2 or reroll on a single action, while the character can keep attacking with the full weapon rating and their apex skill. Simply put, yes, they get a fate point for Disarmed, but it's got more bite to it.
And yes, I'd give everyone at the Christmas dinner table a fate point, because the enemies are, effectively, invoking their being off their guard to get a specific advantage. Though I might get more specific in that actual situation (Wizard's discipline rating stinks because he's drunk, the White Court Vampire's full up on turkey so he gets a penalty to Athletics ratings, etc).
McLane's gun, I think, is worth a fate point because it, specifically, changes the situation in a different way than him just being alone without back-up. The lack of shoes, on its own, doesn't--not until Hans starts going "Shoot the glass!"
Haru said he'd consider McLane having the gun to be a declaration--perhaps one Bruce Willis spent a fate point for. This is the flipside of that.
But put it this way: The shoes
might become important and should be worth a fate point
when they do, but in that situation, having a gun or not having a gun
will definitely become important, so you might as well get the fate point for not having it right away.
Here's something to consider. You award Fate Points when one of your players can't use a weapon for which they've bought stunts. Do you do the same if they haven't spent any stunts on that weapon at all?
I'd look at the situation. If the player doesn't have their Weapon:3 broadsword but can quickly and easily acquire a Weapon:2 short sword, no. If the player doesn't have their Weapon:3 broadsword, can't use their Superb Weapons skill, and have to make due with a Fair Fists rating for attack and defense, then yes.
And what about a werewolf trying to maintain a low profile? Do they get a fate point because they can't change shape in front of a crowd, therefore being unable to use the full range of their powers?
Considering that likely amounts to being unable to use all if not most of their powers, yes--it's either a compel on their high concept, or of the crowd aspect.