Let's start from the beginning. What size battery are you installing? I am going to assume a single Size 24 12V Marine/RV "deep cycle" battery (a normal stock installation). This will be rated at about 80AH(amp-hours). To avoid killing your battery in less than a year, you want to avoid discharging below 50%. This means you have 40AH usable if the battery is fully charged at the beginning of the trip.
If you run a PUP fridge on 12V instead of propane, it draws about 5 amps. So the fridge will deplete the battery in less than 8 hours. Always run the fridge on propane unless there is electric power available (plugged in or being towed). Most PUP (pop-up) fridges are 3-way and will run on 120V AC. The AC will cool better than the 12V DC if available (and propane cools better than AC on almost all PUPs).
The heater fan draws about 4 amps when the heater is running. Unless you have LEDs, each light draws about 2 amps. And your CO/propane detector sucks another 1/2 amp. Even without the fridge, if the heater is in use, you can expect to run the battery down to 50% in 2 nights just with the 12V loads.
To run big draw AC items off a battery through an inverter is a battery killer unless you have a multiple battery bank. Let's say you have a 900 watt microwave (most are 1100-1200 watts). At 900 watts, that's 7.5 amps at 120V, and 75 amps at 12V. Plus, you have a 20% loss in the inverter.
What exactly are you trying to run off the 120V outlets?
2014 Rockwood A122 A-frame with dual golf cart 232AH 6V batteries (116 AH usable)
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time