I will emphasize for those experiencing the dangers of prolonged freeze periods for the first time....KEEP THE WATER TANK FULL!
Now is not the time to take chances. Overheat the coach if you have to because if you break a single water pipe and it is hidden from view a lot of damage could take place, not only immediately, but later if the leak is not detected, and nothing will destroy a coach's value quicker than the smell of mold and mildew.
The cost of diesel fuel to run the generator or Webasto continuously is chump change compared to repair costs. I urge you consider back up also. I used electric heaters strategically placed as my primary heat source but backed them up with other heaters (our propane furnaces on the first coach for example) in the event of a failure. This week we used the toe space heaters as prime, but the Webasto as back up.