Can I charge the house battery with a generator in an hour

No way. Since the heater blower is a battery hog and you only have one battery, don’t use the heater. Use a small catalytic heater to offset the rv’s heat loss along with some extra blankets. We use the Coleman Sportcat. No issues with carbon monoxide but we have a CO detector just to be safe and keep a couple of windows cracked. Works like a charm...