Regarding the machine gun sweep, that seemed like he was directing the thugs fire, and using it as suppressive fire.
I don't think anyone was hit, but everyone else hit the deck, and stopped shooting at him.
That doesn't change the fact that he gunned down all the guys outside.
As for KGBeast, yeah, he's dead, at least til they retcon it to bring him back.
The easily could have/hshould have done the same thing they did with Crossbones at the end of TWS.
But no, Snyder wanted Batman to kill because "he did it other movies."
The Knightmare sequence killing doesn't bother me, nor the gun use, at least if you remove the rest of the killing.
If Batman actually abided by his no kill rule, and they made his inner turmoil about crossing that line to stop the potential future threat of Superman, then the Knightmare sequence has more gravitas, and is about both the fear of an unchecked Superman, AND the dangers of Batman letting himself cross that line.
Instead we get a Batman would is insanely careless, killing everyone in his way during the chase scene, and gunning down the people outside the warehouse.
The worst part about the killing is that you could have cut ALL of the killing, and it would not have changed a god damn thing. That means it was literally pointless.
The definition of gratuitous.
That said, everything else about this Batman was so damned perfect. Which makes the killing that much more egregious, and insulting.