I think you'll be pretty disappointed in the outcome. First the solar part of generation - no output on a cold winter night, and on a hot June day, 300-400 Watts after conversions. Can't speak to the wind contribution, but most small generators don't do better than the solar. So you get 40 A charging your string of batteries. I say string, because your 800 W heater will need about 70A @ 12 V, so, for 8 hours, you'll need 560 AH - call it 8 golf cart batteries to not discharge so low you damage them. So you'll need a minimum of 14 hours strong sun to charge them up, that you won't have on cloudy days, winter days, etc.
It's getting lose, though... maybe a couple more generations of solar improvement.