Sorry for your woes. When people don’t know what they need to know to do something they need to know about…it often doesn’t work out well. I’m glad no one got hurt or died.
I’ve been full-timing for 15 years, first in a small (27’ Class C) camper, then downsized to a 24’ MB Sprinter. I knew nothing, having never been in an RV.
The stories I can tell! My book, Dismazed and Driven — my Look at Family Homelessness in America (https://bit.ly/2ITtkZz) travel tales (nightmares and happy episodes) plus stories of the families I’ve interviewed for documentaries on homelessness.
Plenty of “tricks” make van life enjoyable. My guess is your heater wasn’t broken. It needed a power source (shore power or generator) to operate. The rental agency may have forgotten to tell you (bad!) or you did as I did on my first orientation, spaced out everything.