Re: batting practice w/ rubber mallet
Going from memory as it's been a long time since I messed with the brakes.
On the brake housing, on the INSIDE of it (towards differential) there should be an oval hole at about the 6:00 position. It may have a rubber plug in it. That's your adjusting opening. That's where you insert a straight bladed screwdriver or a brake adjusting tool to turn the brake piston head out to spread the shoes. The more you click (in one direction) the more the brakes spread hence shorter travel to contact with the drum. Clicking that in the OPPOSITE direction will screw down the piston head and therefore REDUCE the spread of the pads. You need to do this to make sure that IF your drums have become grooved due to long use with the same pads, that the pads themselves don't become a flange on which the drum will catch and not let you remove it.
Next item, the brake drum fits over the studs to hold your wheel. In the center you will notice the cap for the bearing. On rear wheels this is typically a concave cap (curving IN) with maybe two half moons on either end. This cap is centered in the brake drum and helps align the drum. The outer flange of this cap is what sticks / rusts to the drum and makes it very difficult to remove the drum. Squirt penetrating oil, WD-40, in this area. If you choose to heat, heat AROUND this and not on it. The reason for that is you want the DRUM to expand, and NOT the cap.
You might also check the openings which the STUDS go through the drum through. Squirt the holes there with penetrating oil or WD40.
Get a rubber mallet or a dead blow hammer. The dead blow hammer is one which has a hollow head usually filled with some sort of lead buckshot or a solid weight that can travel inside the head. When you swing it, the weight travels to the back part of the hammer, and when it strikes, the weight continues moving through inertia and gives a secondary impact milliseconds after the first. This kind of hammer packs a heavy wallop.
Strike around the studs, and the center cap area. Don't strike on the fins, or the outside part of the drum. Because it's aluminum it can shatter, as you've already experienced.
You should be able to see some movement within a few blows. If you still do not, then you may need to get an oversize gear puller, or check with your local tool rental place and see if they rent a hub puller. The puller will grip the outside of the drum back by the fins and push against the center cap and should then remove it.
Last item you will need is a heaping shovelful of PATIENCE.
Other people have pointed out the obvious, make sure the parking brake is off. To check this, try to spin the drum. If it does not spin, you still have some pressure being applied to the drum by the pads, release the pads even more. Once the drum is spinning you can then attack getting it removed.
Good Luck