Hey guys, first time poster here... be gentle

I recently acquired a 5th gen 96 accord sedan lx from some relatives and it has a lot of scratches and dings here and there.

I searched up some stuff on repairing rear bumper dents and I figured I'd fix it myself since it seemed easy enough. I ran into a major problem though, after I opened the trunk to get to the 5 screws on the top holding the plastic bumper to the rear I was only able to unscrew one. The rest refuse to come out and sort of just turn in place like the ridges were smoothed (sp?) down. I've tried just about everything besides ripping the bumper off itself... so if you guys have any advice that'd be great!

PS: If you have no idea what I'm talking about I can go out later and take a few pictures to illustrate.