Educate your wife on catalytic heaters with a cracked open vent and a cracked open window, for cross flow of oxygen. Or get a new wife, without mental blocks. That sounds like blackmail, I know.
They are far more efficient than a forced air heater, which is a huge waste both of propane and electricity. Or buy her a new wardrobe for cold weather.
Another option is to get yourself a more efficient, lower wattage Energy Saving LCD TV. There are several brands, Samsung comes to mind, that consume very few watts nowadays.
4 GC2's on the tongue of a Creekside 20FQ Travel Trailer is probably a poor idea, tongue weight alone. I'd suggest you find another solution.
All the batteries need to be installed somewhere where they are always properly vented outside.
Another option, and one most dry campers consider, is a small generator. If you don't use the microwave oven, a Honda Eu1000i is enough, if you do use the microwave, then the EU2000i would be the better choice. Tie that in with a MegaWatt 30 amp Power Supply unit, and set the voltage for 14.8 volts, maybe 14.9 if it's quite a bit colder. Do a search on how to do it by mexicowanderer.
PS. I am in the same situation as you, in a 2012 Palomino Gazelle G210, 30,000 miles on it, at least, since I bought it.
video of Palomino Gazelle G210