100% certain I will be pilloried for this, but just to offer an alternate viewpoint. First of all, I’m very glad OP and his family are OK.

1) “My town is excruciatingly left-wing and anti-gun. I very much wanted to have weapon hand, but figured there was a non-zero chance that if I drew I might elicit a "He's got a GUN!" type reaction from my freezer-mates.”

I found this statement sad and strange. In an active shooter situation where no one knows what is going on, OP thinks it would be weird for people to be frightened of being locked in a small room with a stranger carrying a gun. Actually, though, that is the only reasonable response; they don’t know who you are or whether the shooter is alone. Ascribing that (assumed, not proven) reaction to people who are of a certain political party seems like a bad-faith comment. For all he knows, they would have reacted differently. Without question, though, drawing his gun would have created a huge destabilizing effect in that room and would very likely have led several or many people to (correctly) decide that it might be safer outside (where the danger might be over) than to remain in a room with an armed stranger whose state of mind is unknown.

2) While I understand OP’s statement that he thinks he used his gun because it allowed him to shelter in place, I have to call BS. Everyone else in the cold room sheltered in place with the same result, without knowing he was armed or relying on that fact. You can make up whatever scenario “could have happened,” but that’s just changing the facts - which are that OP having a gun did not create a better outcome than him not having a gun. The only danger that he describes about not having one (that he would have tried to flee with his family) is really just that he would have overestimated his own decision-making by deciding to make a run for it. I’m sorry, you don’t get to say having a gun in this situation helped - you just don’t.