I think you could keep running the furnace? maybe call back the repair guy and ask? just for safety reasons- to double check.

usually the only part in a furnace that moves to make noise is the fan? so maybe the fan just is very noisey but can still put out the heat for you??

or only turn it on for short sessions to keep a bit of warmth.

but call and ask
does a neighbor have a electric heater you can borrow to keep at least one room a bit warm?