I am not entirely sure I understand which bolt it is, still. IIRC, the brake caliper doesn't attach to the swingarm - it attaches to a sort of carrier bracket, which attaches to the swingarm. Is this bolt holding the bracket to the swingarm, or the caliper to the bracket?
If you go to that parts catalog, and go to the page for the REAR BRAKE CALIPER, is this part #17? If so, that appears to be one of the special pin-type bolts that are common in brakes, and it only has threads on the third of the bolt that is closest to the head. Once you unscrew those, it should just pull out the rest of the way. Could you have it turned far enough to come out of the threads, but the sliding pin section is still in the hole, perhaps with a bunch of grease sucking at it and making it feel like it's stuck, but if you just pulled hard enough it would slide out? Maybe there's nothing really wrong.
Do you have the exhaust off? Can you see what's in there or are you doing this by feel?
I'm not gonna tell you to take a drill to it, until I am sure I understand the issue!