Hi; Just a guess, but I've been where you are with the brake drum. Here's what I suspect is gong on: The old shoes wore into the drum a little and there is ridge at the back edge of the drum that didn't wear. When you try to get the drum off, that ridge catches on the shoes and it sticks. In the process, forcing the ridge part on the shoes compresses them slightly. This is why it freed up a little. If you ever get the drum off you should have it turned to remove the ridge or at least grind it off with your angle grinder.
Rich
