'low voltage' for the leveling system is a pretty 'standard'/common occurrence for many of us, and really doesn't mean a whole lot. If you let the coach remain running for a few moments, the alert will then go off. If you go into MANUAL mode, then it overrides any such alert and you can do exactly as you wish, weather extending them, or retracting them.
as for the 'house batteries', it's doubtful you have any real issue, so unless you are off-grid a lot and are really noticing a very small time that the batteries will support your usage, I wouldn't worry with it. Yes, your 50amp shore power will certainly keep the batteries charged, maintained, and should be no problem, but really ANY electrical outlet of any size will do the same.
two Campers, two Electric cars
former diesel pusher traveler