Couple of questions (spoilers)

Just after Luke got blasted by all of the firepower outside of the mine entrance, there was a short scene with them dragging someone inside and saying they needed medical help. At first I thought it was Luke, but it obviously wasn't. Who was it, and why would they make a point of inserting that scene there?

Did anyone else think that DJ was the actual codebreaker Maz sent them to find, and it would be revealed that the guy they saw wearing the blue flower had stolen it from him? Also, was DJ still on the ship when everything exploded? If he was, and he's dead, you'd think they would've shown us that scene, since he double-crossed the heroes and deserved to die. If he left, they should've shown that too.

When Poe asked Holdo if she had a plan, why didn't she just tell him what the plan was? Seemed like heavy-handed writing just so that subplot could happen.