Welcome to FRF.
If you don't turn the furnace on does the fridge run and not blow the fuse?
Have you pulled the furnace to see if maybe the blower is bound up, or if there's any shorted wires between the furnace and power panel?
As for the jack, have you looked under the frame near the front to see if one of the breakers are tripped. It'll look something like the image below. The little black button is the reset. You press it in to reset it.