I have concrete wall (plastered), 8 mm holes, plastic wall plugs, intact Philips head screws, and a bracket outside.
Accidentally I screwed the screws too tight. They stuck at one point, and won't loosen with the same force. I cannot apply enough force with Philips screwdrivers. Not even with a ratchet wrench (because the head simply pushes the bit backward when turning, and it slips out).
Can not use pliers to pull the screw because I can not prop the tool against the wall (can only prop it against the bracket, which is on top). I tried to use a wedge under the bracket, to strain the bracket and the screws outward. So far, the plaster on the wall would break and collapse. I can grab the higher screw with pliers but can not even grab the lower screw, both screws are stuck.
Can anyone provide some advice?