I think that it would be helpful to clarify on some points of the parking lot scenario.
1. What time is it? Possibly very important.
2. Is the parking lot nearly empty, or very crowded?
3. Are you between him and any possible destinations of his?
No matter how these questions are answered, I would say that the subject should try to move out of the approaching individual's way first, then if the individual alters his or her course to correspond with the subject's new position, that's where it starts getting dicey. In the case that that happens:
1. Can you arrive at your vehicle before him?
2. Can you get into some kind of public establishment before him?
3. Are there bystanders nearby who may assist in some way?
Honestly, no matter how these questions are answered, I can only imagine a narrow scope of possibilities in which the subject should draw, at least if it were me. I am operating under the assumption that the person is reasonable and the assumption that a reasonable person has "not shooting another individual" high on his or her priority list.
Basically, there is not enough information for anyone to give a straightforward answer to the question of "Should I draw and/or shoot in this situation."
Also, I agree that if you are going to draw a handgun, you better be prepared to use it, although that doesn't mean that you
will use it. Isn't it true that most Defensive Gun Use occurrences did not involve the discharge of a firearm? That is not a rhetorical question, I cannot remember if that is true or not
. I seem to remember some people on this forum posting that... Oh well, please give more information on the hypothetical if you want more straightforward answers.