For the first question, perhaps he lost someone in the attack as well? That might motivate him to return.

Otherwise, you're going to have to set up his character so that it is believable that he'd be willing to risk his life. Maybe have him be selfish and unwilling to risk his life only up until a point-- and then make the attack so terrible that even he can't condone letting these people go. He has a set of core morals (buried deep, perhaps) that won't let him sit there and do nothing about it.