There is not a motor-driven bleacher system ever made that could crush a human being. Not only is the motor far too weak, but it is designed to shut off when it meets resistance, both for safety reasons and to avoid damage.
As Sheila Holland is running across the gymnasium floor, just before her high heel breaks and she slides through the blue paint on the floor, there is a clear shot of a man in his fifties wearing blue jeans and a brown coat with a sheepskin collar sitting on the bleachers just watching her run. The storyline had Sean Moran, the 20 year old killer of Sheila Holland as the only other person in the gymnasium.
Delko and Simmons are worried because they only have two tries to find a password before a hard-drive is erased. Since they have a copy of the hard drive, they could make other copies and try as many passwords as they wanted.
At approx 17:30 Horatio tastes the substance that the doll head is made of and says it is Heroin. No self respecting police officer would do that let alone a CSI. That could be laced with poison for all he knows, and that's not even considering he may have to take a random drug screen later that day.