GD,
After I drained the water heater I stuck my garden hose in and blasted the debris from the anode rod out. After flushing a couple of times I just let it drain, replaced the rod and buttoned it up.
As far as keeping the coach warm {mid fifties} after winterizing and eliminating water and adding RVAF... There are lots of components in a motorhome that do not do well in freezing temperatures. When things freeze they expand/contract. Seals can be compromised and control boards and other sensitive electronics can be damaged. IMHO: it is far better to keep a reasonable temperature and this is easily done. While unusual that forecast for a low of 25 can easily become single digits while you sleep.
As to keeping my fuel tank full it is simple... I always do. Any possible condensation is greatly reduced and the coach is ready to go at a moments notice. As noted we will be taking off in January for a week or so and perhaps sooner than that. Gas prices have risen about 25 cents a gallon since I topped it up after our last trip so that is working out nicely as well.
Even when fully winterized we can be gone in about 15 minutes as all we need do is fill the water tank, load a few groceries and turn the key. This mode also works during fire season as well as short notice for an evacuation could easily take place.
As always... Opinions and YMMV.
:C