To your first question (other things to watch during that long interval before the game). Look for court irregularities (things hanging from the ceiling, supports or straps from the backboard that the ball might hit). Go talk to the cheerleaders to make sure they know how much room the crew will need during the game. Watch what the teams are practicing because it's often a clue as to what they will run when the game starts (if the 6'8" center is only practicing 3-pointers, he might not be an inside presence).
And like you already mentioned, find the cutest mom in the stands. See if there are marked coaches boxes. Is there an X on the floor for subs? Are the team's chairs too close to the floor? Are the chairs set up too close to the scorer's table such that the coach is already out of the coaching box when he stands up? There are many things to do to keep your mind occupied.
To your second question. If the player seemed shook up, let the coach sub. We're looking for trouble when we start trying to diagnose the severity of an apparent injury.
Z