Heat. How how hot does everyone allow? Tire heat sensors?

Everything will revert to the ambient temperature.

 

So youre saying heat index and wind chill is not worth mentioning when broadcasting a weather report?

 

Yes. Unless you’re naked and outside.

 

Pressure is what I would be monitoring most closely. It will usually say on the tire what the limit is; or you can look it up based on whether it's a load range G or H. All bets are off with recaps though.

 

Maybe it has something to do with the volume of air inside the tire.

It is the tire that heats up due to friction, transferring some of the heat to the air inside the tire.
A lesser volume of air will absorb less heat, leaving more heat in the tire rubber.

And is air compression linear or exponential?
Is 100psi twice the amount of air as 50psi, or actually more?

 

100 psi expands more then 50 psi.

 

I just go by what the people who built the tires recommend.
Truck & Bus Tire Pressure | MICHELIN COMMERCIAL TIRES