I really tried to search into existing threads before creating a new one and closest I could find is this: Should ceiling fan mounting screws thread into the box or the framing behind?
Unfortunately, I didn't see a clear answer. But the scenario is pretty similar, my home is supposed to be pre-wired for installing a ceiling fan but they only installed a basic light fixture with two bulbs, after removing that light fixture, I was expecting two MACHINE screws going into the electrical box (like in other light fixtures I've replaced before), however, instead, there were two WOOD screws that I had to remove in order to remove old bracket.
So I'm suspecting the electrical box is something similar to this kind (the first two pictures in the album):
If you scroll further down in the imgur album, there are actual pictures of my box and the two wood screws I removed.
The box seems to be still very well attached/secured after removing those two screws and after cleaning up the paint a little bit, it actually does say "ACCEPTABLE FOR FANS UP TO 70 LBS" (i only need "acceptable for 35 lb fan") so I'm thinking making a hole in the plastic box and loop around the secondary support cable from the fan motor.
But my main question is, can I reuse those two wood screws I removed to install the new ceiling fan bracket as long as I get a good torque when re-tightening? or what should be the approach here? Should I replace them with slightly bigger diameter screws and hope I don't have to replace that fan again in a very long time? Should I replace the electrical box with a different kind with machine threads/nuts? (probably not easy as the attic is "flooded" with blow-in insulation).
Thank you in advance for any replies!