Hi, I don't know if you've solved this yet, but I just did the same thing Friday night.
After a couple hours of pulling (with the Moen tool), twisting, squirting vinegar and Liquid Wrench into the cartridge, miraculously the thing came out. One of the rubber pieces on the side was stuck to the pipe. These things are a real bugger. Sheer force is the only thing that will get this $%^#@$ out. Good luck!