Toilet repair

Buy, borrow or rent an impact driver to free it up. Or try a Robertson (square head) screwdriver and lean on it and use Visegrips to turn it. Turning it back and forth can often free them up. Also, tapping it with a hammer using the correct screwdriver or with a punch can sometimes also help to break it free. Should only be into OSB or plywood and shouldn't need gorilla force. Shouldn't grind the head or cut it off unless it is severely rusted and is the last resort.

Some toilet flanges are glued into the tank and some screw in.

Are the screw heads big enough to use a Dremel with a grinding wheel or cutting disc to make 2 flats 180 deg appart to allow a small wrench or crescent wrench to turn them?

can you just drill the head off of it? Then you could remove the toilet and use vice grips on the stub of the screw to pull it out

Mark and Linda wrote:
Have you tried using a square head bit with a small socket and a ratchet. You might be able to put more downward pressure on it. It might be a number 2 or 3 tip....can you get a pair of vise grips on it? Just some suggestions....

I thought I would drill a hole in it and use an easy out

Square (Robertson) bits come in up to 5 or 6 sizes.

Have you tried using a square head bit with a small socket and a ratchet. You might be able to put more downward pressure on it. It might be a number 2 or 3 tip....can you get a pair of vise grips on it? Just some suggestions....