1: A 120 volt ceramic heater doesn't outgas (other than burning off any dust or factory oil when it is new.) However, just make sure to place it somewhere where it won't get knocked into flammable stuff. Nothing wrong with it, although I prefer forced-warm-air heaters like Vornadoes.
However, the propane furnace is better since it will vent warm air on the tanks, keeping them from freezing, while an electric heater will just keep the coach area warm.
2: It will work pretty well, but having a fan to circulate air will help a lot. Even a battery powered O2Cool that is used to blow warm air from the ceiling back down will come in handy to keeping everything evenly heated.
3: The RV furnace sucks air from the outside and exhausts it to the outside. The air in the RV goes through a heat exchanger, and never contacts the air the RV furnace uses. No venting needed.
4: I've burned through two 20# bottles on a weekend in low 20s weather, however I had the thermostat cranked to 78, so it was expected that the furnace would be chugging on the tanks.
I like using the RV furnace just because it gets the whole rig heated, as well as the water tanks. However, propane might be hard to get, and if on hookups, electricity is included with the bill, so one might just use an electric heater.
