Heres my usual way of dealing with rusted on drums. Put lug nuts back on flush with end of lugs to protect threads. Clean around the base of all the lugs and the large center hole with a smallish wire brush. Soak everything with a good penetrant- base of lugs, center hole and all small holes in drum flange. Start tapping on drum flange between all the lugs. Do that for multiple cycles, letting it soak for awhile between. The last function is to hit the outer flat face of the drum straight in with a large dead blow hammer or with a 2x4 and a heavy regular hammer. Hit and turn, hit and turn around the drum face. Not too hard but reasonably solid hits. The impact will usually loosen things after a fashion like when you removed the drum holding bolts. Patience and persistence will usually win the battle. Of course if that doesn't work or you're not up to it then fall back to Jerry's method. Like he said you probably should be or need to pull the hub anyway.
