I still think you can get it off. Put it in as low a gear as you can and it will most likely break the adhesion to the drum. I don't hink you can hurt it. Then you will be able to pull the drum. Don't toss out that broken bolt, you may be able to fix the adjuster. I will take a picture of a backing plate so you can see what is goin on.

I would pull the drum off to see what it looks like in there and clean up the linkages, check for hydraulic leaks, and fix that darn adjuster. I can almost gaurantee that you are going to have to clean up the linkage so it doesn't stick. That might be part of the problem. I had the exact same problem you had so there is hope yet.

A day without laughter is a day wasted- Charlie Chaplin
When wrestling a grizzly bear, you have to keep at it until the bear gets tired, not when you get tired.
1948 Chevy 2-Ton