You are welcome. I write technical notes in my work, though this is a more casual style.
The drawers under the bed: We have two drawers above an empty opening. We've found a couple of containers that fit under there for shoes and coats that we wouldn't use often but like to have with us.
Regarding the freezing weather - even having fresh water in the tank will freeze if the temps are below freezing for any length of time and you are not running the heater. Even though the space under the bed is within the insulated envelope, the insulation is R-10 at the best. A house with 4" walls is R-21 for a bit of reference.
If you'd like to flush the toilet during the winter, I'd suggest carrying gallon bottles of water. Then add some pink stuff to the black tank from time to time to help keep it from freezing between the times you empty it.
Our temps in western Oregon typically range from 50 down to 20, with an occasional drop into the teens. Some winters never freeze, but the last several years we've had freezing nights for perhaps a quarter of the fall/winter season. If the night is clear, the temps usually drop into freezing temps. If they are cloudy, usually the temps stay in the high 30s to 40s depending on the weather pattern.
Formerly: 2000 Four Winds 26Q/Ford, '96 Kit Sportsmaster 22' 5th wheel, '91 Sunlite truck camper, Wildernest flip-top canopy