If worse worse to worse and none of what has been mentioned works...do as mrfixit just posted then get a big prybar and start prying and heaving on the drum......sont worry about damaging the shooes as your going to be doing a complete brake job after you get the drum off anyways(i hope?) jam the prybar between the drum and edge of the backing plate might damage the backing plate some but this MAY be the only way to get the drum off...