Using 1600 ISO for stills unless you have a fast moving subject you need to capture would be silly, a waste of the excellent gimble stabilisation. You can get away with up to a couple of seconds exposure time in a hover in still conditions. Use the lowest ISO you can for best IQ.Still or video? I'd try these:
For stills: iso1600 (3200+ is unfortunately "fake"), f2.8, raw. If still too dark, shoot a burst of -2EV frames and do a median stack +2EV pull in photoshop later.
Video: f2.8, 24fps, iso 1600 or 3200, beyond that you'll need a night vision camera...