After spending two days in the house turning blue by 50F (+/-) degrees inside and subzero wind chill outside, I finally called the guy who came and installed a brand new boiler and, this morning, the house is human-friendly again. I still had to sleep with socks and four thick blankets in order to keep from shivering.

This is the fan/blower unit that blows hot air into our garage (read my workshop):

As of 1 this afternoon, the garage and house feel totally comfortable again!