Plot hole: Det. Kerry says at the scene of Paul's trap, "He had two hours." There is no way she could have known that. The clock simply said 3:00 and the tape specifically says "you have until 3 o'clock or this room will become your tomb". No way to know that's two hours after the fact.
Plot hole: Jigsaw is lying on the ground with a gun in one hand, and a tape recorder in the other; the tape recorder is removed, leaving his hand empty. If both of his hands were occupied/exposed, he would have had no way of depressing the button on the remote control to shock the prisoners. As seen at the end, when he shocks Adam the final time, the control is in his hand, not hidden anywhere else on his body.