I just drain whatever I can, next day or later in the day put the plug back in. Freezing in the tank with a little water never broke it. When dewinterizing, you will flush the tank, and fixtures, then sanitize it. So the old water gets flushed out.
I use mine in the truck for a small pankake compresser. So that goes with me on longer trips. I can air up tubes, kyacks and tires. Other then that, i use it to plus in my electric ac/dc cooler when traveling.
You need to check the saftey switch first. If its only the overhead lights. If its not under say the swing up gally, some have them by the bunk ends. Also check the wiring harness that runs outside the camper, usally the drivers side rear of the pop up canvas.
Do you have room in the bed of the truck and get the mat that goes over the tailgate? Front truck receiver for bikes. Or just get the correct mount if you have the capacity covered. So many ways to carry bikes.
I can't see how much space you have to work with, but maybe a hard pipe pvc coming down and off to the side. Zip tie it in , or use clamp fastners. Add a full throw ball vave near the end. That may work better, or the same as the flex hose. I figure better since it should stay tight without...
So start there. If the air was thinner, it may effect the switch. A limit switch/rollout switch activates by heat. So, it could be bad, or the higher altitude produced more heat because the air wasn't moving out the flue fast enoug activating the switch. Its an easy enough part to replace.