You haven't mentioned removing the 2 screws on the face of the drum that hold it in place. As for the pinion adjusters, they are very fragile and although they may be turning they may not actually be loosening the shoes. I've had to press on the shaft of the pinion with a big screwdriver, forcing it in towards the outside of the drum while turning carefully with an open end wrench in order to adjust the shoes. Be careful with those drums as good ones are hard to find.
