I've had to use small chisel, carefully aimed at outer edges of slots to start it turning. It messes up screw and will need replacement. Lots of penetrant and heat works too. Sometimes the impact tool works, not always. You can pull the drum and hub as one by removing the axle and big nuts. You just doing brake job? That way hub is out of way for brake work too. You should put in new rear hub seals if you do brakes anyway.
