BRAKES

There should be a rubber plug in the backing plate that can be removed. An adjuster wheel can be then accessed. You may be able to get a flathead screwdriver in there to turn it, it will need to be turned the way it doesn't want to turn. It may also be frozen.

Try this first: Use a 3 pound hammer and whack the front of the drum between the studs with good hits, It may pop it loose. Then you can hit the drum edge towards you at various points. You may be able to just pull it off by hand at this point by rocking it and pulling towards you.