re: cooling tektites
The problem as I see it is that the ejecta can only lose heat energy when it comes into contact with a gas molecule, or it is hot enough to glow and emit photons. Once it stops glowing it can still be hot enough to deform and in a near vacuum the number of gas molecules is much lower.
It does raise on interesting point. If these aren't tektites then why are there no tektites? If the reason is the inability to transfer heat then the molten ejecta should splash down and we should see evidence of that around these craters. If we see that we differentiate it from the spherules.