(click to enlarge)
To answer your questions:
1) Yes, I am actually a seatbelt engineer.
2) Yes, it is possible for seat belt webbing to cut you if it routes over your neck. It's not common though, because...
3) Yes, we check the vehicle design to make sure it's routes so that this won't happen to most people.
4) Yes, given all that, it was Becky, Michael's speech therapist, who figured out what gave him the cut on his neck.
(It was a real high-point in my career, let me tell you!)