The blood and the head wound were both real. No assistance was necessary from any razor blades or fake blood. I'm not even sure they rubbed up the spot before the match, though he may have used asprin or another blood thinner. The shot he took would have opened him up either way. He hit the spot on the angle brace going between the back and seat of the chair when Edge slammed him the second time. That brace is a straight metal edge, unrounded and often a bit course. (I've set up plenty of chairs like that over the years to know that you keep your hands away from there.)
AFA the amount of blood...head wounds always bleed more than others because of the simple fact that the blood vessels are closer to the surface. The fact that Shawn kept getting hit was why it continued to bleed so long. You could watch and see it starting to clot up. Then, he'd get hit again and it would renew the flow. If I had to guess, I'd say he lost a good pint and a half of blood by the time the match was over...if not more.
As for the concern about HIV, etc. With the physicians and trainers that the WWE employs (even a plastic surgeon who travels with them to take care of wounds like this), I'm sure they must test on a regular basis. I would imagine it's part of a regular physical exam...and not just a yearly one like most folks get.
Vigilance about things like this has been much higher since the incident when Greg Luganis (SP?) cut his head open and bled freely into the pool during a dive at the Olympics back in '88. The fact that nobody knew until later that he was HIV positive put everyone on notice. Regular testing in most sports where the athletes tend to get banged up is pretty much a given these days. Many other sports have followed suit as well.
After saying all that, can I tell you that Shawn and others absolutely get tested? Nope. I can't. I think you'd have to be in the business to know for sure. But, I'd be extremely surprised if they didn't.
Ann