I'm with racer here; I'm not letting him get within 6 ft or entertaining a conversation if I can at all help it. To answer your scenario questions:
Q1: Confront him verbally to go away, back off, leave you alone?
A1: Yes, well before he's within 6 ft of my person, car, etc., I will confront him verbally in as forceful of a tone as I can muster to "Do not approach any closer, back off, and leave me alone" WHILE I assume a defensive/bladed posture ready to execute a scoop draw.
Q2: What if he continues to aggress on your person?
A2: He's already been warned and continued to approach despite my warnings not to, then I'm now in reasonable fear of imminent threat and I can articulate that I he has nefarious intent and I'm in reasonable fear of GBH or death!
Q3: Will you allow him to get closer than that 6 feet?
A3: See above.
Q4: How will you enforce that distance if he moves closer?
A4: I'm now putting my vehicle between him and me and as I've already been convinced I'm facing imminent threat of GBH, I'll be at least placing my hand on my firearm and getting ready to repel boarders, if not drawing and issuing one last warning!
Q5: Threaten grave bodily harm or death upon him by announcing your armed and will defend yourself if he closes on you?
A5: If he continued closing the distance, then I can articulate that he's met the definition of an "Imminent threat" of GBH or death to me.
Q6: Can you even draw and fire your sidearm before he can reach you and wrestle for the firearm if he decides to?
A6: That's the reason I will do my best to prevent him from getting anywhere near 6 ft of my person and if he has continued to close after being warned not to approach any closer, knowing I'm alone in an empty parking lot with an imminent threat approaching, then yes, as I state above, I already have a reasonable fear of imminent threat of GBH or death, I am in a place I'm lawfully allowed to be, and have no duty to retreat in Florida, then I will draw my firearm and if he hasn't already stopped, fire on the attacker, COM until the threat changes shape or catches fire!
Immediately after the encounter, I will be draw my cell phone to 1) call the cavalry and report the incident, and then 2) call my attorney.