Where might you be located? :-)
Couple things to help with getting as much out of everything as possible.
Cell phone, if you haven't already, go find a car type charger, 10 times better for charging directly than the wal wart and inverter.
Same goes for Laptop, unless it's real new, there's car adapters that will charger laptops much better directly connected to 12Vdc source than setup DC/AC inverter then step down AC/DC adapter.
Furnance, go see if it has a startup cap on it and what the hp rating is.
If it's an older unit that uses a pulley, then you can certainly find a 1/10hp DC powered unit to replace OR put an inverter at it for startup. These are easier to startup than a fridge, but barely. IF using a DC motor there could be a problem if your unit has a thermocouple.
If these are truely ARCO panels; then they at one time, were at the top of the heap. Those panels have a pretty good 20 year life span.
Now the Battery: Marine batteries are pretty good for getting your feet with and will last a long time on good loads, however if you can, go find some of the golf cart batteries They're likely 6Vdc and you'll need two. Sam's has them pretty cheap, and the ones a neighbor just got are 220Ahr, so for the price he got a much better deal than expected.
AND they'll give longer creature comforts :-/
Above all else have fun with it!
Bruce S