I'm still on the first 30# of propane after 8 nights of boondocking. So running the fridge on what you've got won't be a problem. Just watch running the water heater unnecessarily.
If you're not running the heater or TV, you'll probably have enough in the battery for 2 days at a time.
A 120VAC genset will have the battery back up within 3-4 hours.
But, if you absolutely need the A/C or microwave, only the genset will run 'em.
The other advantage to the TT: Evenings with no bugs! Light a small citronella candle inside and keep the other lights low. It is so nice to sit and talk, play games, read, etc. without the incessant swatting!
Definitely, throw 20+ gallons of water in the tank and run the pump. Charge the lines. Fill the water heater. Then turn off the pump and dump the tank.
TT 2015 19RD "TheJayco"
TV 2003 F-350 "Montblanc" - Housebroken chore truck
Sitting in The Cheap Seats.
And proud of it!