Have any of the companies done an honest-2-god btu assessment - volume
of the house, surface area of exterior walls and ceiling, surface area
of windows and doors, etc. ? Without that the whole calculation is BS.

I had a 125k BTU super efficient in my last house, which is in the
midwest and gets really cold in winter. That house was bigger than
yours and though was insulated, leaked like a sieve and had single pane
windows (fricking historical society).

You're in Oakland. The average temp in Jaunuary is 50. How much
goshdarn furnace do you need ? Have you gotten a single estimate from
someone who spend 2-3 hours measuring things ?

I bet your 50 year-old jobber was less than 70%, more like 50-60.

YMMV.

Warranty companies es teh suxx0rz.