"Dave" wrote in message

1) What is the purpose of running the low speed fan? Is it for more
even heating throughout the house?

Mostly, increases comfort, minimal temperature swings.


2) Does this save on gas (i.e. will the furnace burn less often?),

It may, but I don' t know for sure.


how many watts is the fan on low-speed?

Look in the manual for the motor rating.


In my case, the air circulation includes an uninsulated basement,
whereas the thermostat is on the main floor.

Insulate it and save a bundle.