Okay, I tried to bend it back into shape with fat-nosed pliers. Didn't help with the unscrewing. I tried jippiejee's suggestion, to no avail. But after bending the rim back, the smaller half of the glass came out, and I managed to pick the rest out with the pliers. Then I proceeded to try and twist the rim off with a wrench, then with the pliers, but I ended up bending it to shit and pulling the threads apart, but I got it off. I was working so close to the lens, trying not to scratch it, it was painstaking. And trying not to twist the focus further than it should be twisted, it was the closest thing to brain surgery I've ever gotten, and hope to ever get. Especially considering I was using rusty woodworking tools from my shed.