You can change display settings in the registry editor, at the following location :
HKEY_CURRENT_USER\SOFTWARE\RawThrills\Nerf\
But unfortunatelly that game does not resize the content to the window size.... it must be hardcoded somewhere that everything is done for 1080p, so changing the resolution values will only result in "cropping" the real 1080p content to the smaller window size display
Sorry but I don't have any clue....
If the plugin was shot down by Unity Engine, controls would not work at all
Having 1 gun controlling 2 sights might be DemulShooter not connecting to the plugin (default behavior without DemulShooter is mouse cursor control for both gun, and left/right buttons to fire P1/P2 gun) but it cannot happen during the gameplay, even if DemulShooter closes itself