Re: I think I need some help.
I have had this situation a few times. I have removed the head of the difficult screw, or screws with a drill or Dremel. You can then lift the mount off and can use a vice grip to get a solid grip on the protruding stud. The mount may not be usable after doing this. If in doubt, I'd bring it to a gunsmith.
"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt