Dave,
The screw you can't get out shouldn't come out! It's a eccentric screw for point gap adjustment and I believe it's peened on the underside of the breaker plate...it doesn't hold anything to anything, only turns!
From your pictures it appears all the screws have been removed so the breaker plate should come right out. It probably won't 'fall' out, you may have to take a hook of some sort and persuade it, but it will come out...if you hold your mouth the right way.
Stuart
