Kleanbore, since you reject alternative B (stopping the threat with your weapon), you must be choosing alternative A (hand-to-hand combat).
No.
The scenario permits only these options.
Well, yeah, but one cannot really have a serious discussion about an unrealistic scenario--one which I think has been framed in a silly manner. There's nothing in the scenario about escape not being possible, and one could certainly leave, and should, stand your ground laws notwithstanding, if he values his safety, his record, his fortune, and his personal freedom.
If for some reason my egress were blocked (not mentioned in the scenario), in my case the guy would wind up with a face full of oleocapsicum (not permitted in the scenario).
But if escape is not possible, yes, as much as I dislike "hand to hand combat", I would use physical force to defend myself against physical force (no "fair fight", no use of my knuckles), concentrating on retaining the weapon he does not know I have and on avoiding contamination by his bodily fluids. One would not be trying to knock him out, hitting only from the front and above the waist. A kidney punch, gouged eye, injured ankle, or dislocated shoulder would end it. Better that than facing a very steep uphill defense against a murder charge after using deadly force to defend against physical force. Much better.
But not good. Therefore, (1) escape and (2) less than lethal implements of defense.
None of us like the idea of being pounded upon, but legal minds have wrestled with this problem extensively since the twelfth or thirteenth century, and oddly enough, they have kept coming up with about the same answer.
In the scenario as crafted, in my case the obnoxious gentleman would be an overweight sixty six year old--not likely to start something, but hey, that's the scenario.
(Added) I stay out of bars and places where I am
likely to encounter trouble. However, if trouble happens, I think it's more likely to come in the form of someone younger and more fit, and probably, more than one person. That brings in disparity of force--part of "A" in A, O, J. However, I'll still go with "ADEE" and less than lethal implements before resorting to deadly force unless the assailants are clearly armed.