I did something slightly stupid when preparing to mount a new fixture to a very old unused ceiling pancake box in a 96-year old home: I unscrewed the bracket that attached the mounting nipple to the box, under the assumption that I would be able to either re-screw it back in, or attach alternate mounting hardware. Instead, it seems that there were nuts holding in those screws, which are no longer aligned with the screw holes, rendering them useless as attachment points. I see no other obvious way to attach any kind of hardware to the box.
Ripping out the box will mean doing some violence to an old plaster ceiling that I'm probably not up for in the near term. Wondering if I'm missing some other option?
(ps, I know it's controversial to attach fixtures to old two-wire circuits. If it helps, I plan on updating the circuit breakers to Arc Fault Interruptors, and only use LED lamps in this fixture.)