Bruce refocuses more on Zerxus than his father temporarily, head cocking over at his response. This man is going to give him a literal pain in the neck (if that were possible) at this rate.

Yes, and that certainly explains some things about his presence here..

"How long is this going to take you?" He sounds impatient. He isn't, really, it's just a means of prodding Zerxus out of a... revealing reaction, for reasons he can't quite explain. He just knows he's uncomfortable with it.