IANAL, but my understanding to is that there is a distant difference in the eyes of the law between a "display" and "discharge" of a firearm here in TX. You are allowed to display (which is what the OP did) a firearm in any situation that you would be authorized to use "force" (such as punching the dude in the face). And depending on the jury, and the expertise of your lawyer, you likely be able to make a good case for use of force against two (or even one in some cases) persons continuing to approach you after you've given them fair warning to stop advancing on you. If you are and older person, slightly build female or it's late at night (etc....) and the person(s) approaching you is a big hulking male, you are probably MORE LIKELY to convince a DA or jury that you were authorized to use use force and you had a legitimate fear that the approaching person intended to harm you. However, that will ultimately be up to the jury. I DO NOT think that you would EVER be authorized the "use of force" (such as displaying your firearm) unless you have given fair warning to them to stop advancing on you if they have not made any overtly aggressive move towards you. In any situation, you would likely NEVER be authorized a use of deadly force (a discharge of your weapon), unless there is the threat of deadly force against you by the person, which would usually require a weapon to be displayed against you.
I would ALWAYS caution even DISPLAYING (which includes everything from showing it to pointing it at the threat) firearm, even if authorized to do so by law, unless absolutely necessary. If not for the legal ramifications, the simple displaying of a firearm by you, could represent the threat of "deadly force" to the person advancing, or even the not so aware LTC person pumping gas on the next pump over. In general, I would think that displaying a FA should be considered a last resort option in this case. Hell, if I was pumping gas like in this scenario, just remove the nozzle and threaten the dude with a solid dousing of gas or even a good ole fashion TX ass-whumping
if he came any further would deter anyone not intending to do you harm.
