For example if you watch the Albion "how its made" video and listen to many other bladesmiths they say they use a concentrated gas torch on the end of the tang and peen like that. That way they don't spread heat through the blade and destroy the post-quench hardness.

I've heard both cold peening and hot penning are historically accurate (true/false?), if so, how did a medieval swordsmith manage a hot peen? They were working with large, well-dissipated heat sources, nothing that could heat a 1-3 inch spot to forging temps while the rest of the sword remained room temperature.

Was the pommel installed BEFORE quenching..?

It´s no problem really.
Deflect the heat from the areas you don´t want to heat.
A piece of thick sheat Iron for example.
And wrap the areas you don´t want to heat in wet cloth and work fast.

/Viktor

So the heat doesn't "conduct" down the blade much?

Even with my 3/4" burners propane forge I worry about undesired tempering in steel within proximity to a 'hot spot' I'm doing

It seems like it would be really difficult in a coal or similar forge, back in the day

The wet cloth is definitely a good idea, I must try that

Heating the last inch or so of the tang in a coal fire without significantly the rest of the blade is no problem. The steel conducts heat, but not very quickly. Heating a plain carbon steel upto 200C (418 fF) or so will not significantly mess with the temper.

Another thing to consider: a little heat in the tang might soften that area in a beneficial way. Some tangs were less hard, unhardened altogether, or even made of softer iron.