I don't think Kirk stole the show in the battle scene. Sure the Enterprise made it possible for them to survive but Khatami and the Deltan captain whose name currently escapes me (sorry) dominated that scene. We have them risking their lives through the entire battle; if not for them, there would have been nothing left when the Enterprise arrived.
As for Reyes, he didn't KNOW the colonists would be killed he only knew it was a dangerous situation. He had no way to know the situation would escalate to the point it did. Besides, what more could he do? he couldn't legally prevent the colonists from going there and he would have been immediately arrested if he told them why they shouldn't go. Even IF he told them the whole truth, his ex probably wouldn't have listened. it was only after the massacre that he realized that the Shedai were enough of a threat that the truth needed to be known.
I honestly can't see how Reyes could have handled the situation better, especially when most flag officers in his situation would have kept the Shedai a secret even after the massacre. I think he showed more courage and heart than others would have.
Besides, part of the series ending is some people got what they deserved and others didn't. Poor Zeke didn't get the ending he deserved. That's just reality.