The second shot in Kuma's killing could not have happened as shown. A revolver works by rotating the cylinder as the trigger is pulled, dropping the hammer on a fresh cartridge. The gun was dropped without a second trigger pull, meaning that the hammer would have fallen harmlessly on the already expended cartridge.
When Monroe and Rosalee go to Nick's, to explore the tunnel, while Adalind is at her job interview, they would have obviously driven there, as they did not expect Adalind to return home until late in the day, and as such, they would have had no reason to hide their vehicle. However, when Adalind comes home early, and Monroe and Rosalee are forced to hide, that really doesn't make much sense (and is never explained), as Adalind would surely have seen their vehicle, and known that they were there.