You would be lucky to get 30 minutes of heater running time from a couple of lead acid batteries. A simple approximation of DC input in amps to the inverter is 1/10 of the inverter output in watts to an appliance. But that 150 amps will pull the batteries down as they are rated at 1/20 amphour draw and 150 is almost ten times as much which probably pulls then down as if it were a 500 amp draw.
The TV would work fine depending on size. I had a 19" LCD TV that pulled 4 amps DC but yours is probably bigger, so maybe 6 amps or so. You could watch TV for 15 hours before you got down to 50% of your battery capacity which is the limit for decent life. A blender is very short usage so no problem with that either.
But forget the heater, use the propane furnace which itself pulls about 4 amps DC to run the blower. That will give you about 24 hours of use with your batteries but I bet you will be cycling at maybe 25% so up to 100 hours of furnace use on your batteries.
David
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