I'm not sure I'd want to have a heater that I plug into my 12V power supply. Running a heater all night off your vehicle battery and then finding out you don't have enough juice to start your vehicle in the middle of nowhere is not my idea of fun.
Also your concern about a propane heater is very real. Campers die from heaters improperly vented every year. But there are a couple that are OK. This is the one I would use if I were going to tent camp. https://www.walmart.com/reviews/product/5712813
But I would also make sure I had my window flaps open a bit to let fresh air inside.