Don't try to light the beast unless you understand perfectly how the boiler controls work and can rig it to work safely.
Even old-skool boilers have interlocks on the ignition & flame sensing to keep the gas off when not in an ignition cycle or during a flame-out condtion and if you defeat those interlocks you're putting yourself at all kinds of risk.
It's not exactly THAT cold out. Turn on all of the lights in the house and freeze-up will be unlikely. Don't try heating with a fireplace, as that will heat the room it's in, but draw cold air into other rooms increasing the risk of freezing pipes, etc.. Buy an electric blanket for sleeping.
If it's under 40F upstairs at night and you're concerned about a top floor bathroom freezing up, assuming your hot water heater still works, fill the tub with hot water and close the bathroom door.
I went 10 days without power a bit over a year ago, when it was getting down to 10F several nights in a row and managed to avoid freeze up with select use of hot water and gas range burners. WITH power it should be dead-easy to avoid freeze-up with overnight lows only in the mid-20s.
With oil-filled radiator type electric space heaters you can probably even keep a few rooms comfortable with low fire risk, low noise. Friday isn't that far away.