Its a really big job to upgrade your batteries to accommodate that blower. I have 4 Trojan T-105 batteries (the big expensive 6 volt batteries) and 600 watts of solar panels, and I *still* don't have enough power to reliably power my furnace blower over night. The things pulls 80 watts, which is just crazy for an RV. I'm surprised these are used in RVs at all.
My solution was to mount a Buddy heater on the wall. It costs all of $80, and is "tent safe". Get a CO detector of course and crack a window. And plumb it to your propane tank so you're not using little bottles of propane.
My heating needs are pretty easy since it doesn't really get below 40 degrees where I live, but you could always get multiple Buddies, or go the cadillac route and get a Wave catalytic heater:
https://www.amazon.com/Camco-57331-Olympian-Wave-3-Catalytic/dp/B000EDQR8M?th=1
Note that they have different capacities at that link.
They mount beautifully on a wall. Aim a fan at it if your rig is large.