Question: In the automated car garage, why did Hendricks jump to his death holding the briefcase rather than just dropping it down?
Answer: As a way to prevent Ethan from quickly stopping the countdown. It's a big distance Ethan would have to drop in quick amount of time in order to stop the detonation. He was most likely going to die, so he takes his own life in order to (unsuccessfully) prevent Ethan from stopping the detonation.
Yes, but it's the same whether he 'accompanies' the briefcase or not. He rather wants to die now than be captured by very pissed-off people and experience a nuclear war.
Answer: Knowing he was trapped, he may not have wanted to be taken alive, preferring death over capture.
raywest ★