Gary, if I were in your shoes, I'd be setting that thermostat up some to at least 55 or maybe even higher. Those water pipes are nothing to be messing with! If they break someplace inside and under the floor, you may have a real problem!! You didn't say what year the unit is but no matter which year it is, there is heat going into the underbelly and/or basement to keep those water pipes warm.
If you don't have any vents going into the basement, I'd put a small ceramic heater in there on low just to keep it warm enough to keep the pipes from freezing. I don't know if you are hooked up to city water but if you are and the hose is not wrapped with heattape you will have a problem there also. I'd be unhooking the city water line and use the fresh water tank for the evening or until the temps warm up anyway!
The galley tank dump handle is possibly one of most asked questions on here and I have no idea why Keystone does not mark the valve handle more clearly or atleast put it in bold print in their manuals. New owners are always asking about it. Even some of the salesmen or dealers don't know about it! Weird!!
Good luck and be sure to ask away if you have any questions! There's never a question that cannot be answered by someone here on the MOC forum.