Normally with this kind of setup, the wood stove would be considered your primary source of heat, not an auxiliary source. Its output is directed through your electric furnace just as a means of distributing the heat via your ductwork throughout the house. Based on your other question, the thermostat fan/limit switch ensures that as long as you've got a fire going, the fan will be running and distributing heat.
If you're not burning a fire, or it's really cold and your fire isn't keeping up, the furnace thermostat on the wall will tell the electric furnace to kick on and take up the slack.
Anyway to answer your specific questions:
Q1: Yes, this sounds reasonable.
Q2: Sort of. The wall thermostat will keep your house from getting too cold by turning on the electric furnace. There's nothing keeping your house from getting too hot, but then that's part of the charm of heating with a woodstove. You can always open a window (as you mention).
The furnace doesn't care what the temperature of the air in its plenum is, it will only turn on when the thermostat on your wall indicates the house is too cold. The thermostat on your stove, however, is measuring your stove's output air temp and if it feels warm air it will start blowing it. So expect it to be on for as long as you've got a fire burning. You could plug your stove thermostat into a switched outlet if you wanted some control over when the fan runs and when it doesn't.
Call suburban, tell them that you don't want the tanks any more.
Make sure you are present when they unhook so there is no damage to your connection.
I recommend that you use a pair of tanks, so that there is always a spare on hand. One is disconnected and capped. (Bugs love to nest in the opening...)
Note that for emergency heating you can go through a tank of propane in a hurry. There may be merit in buying your own 100 lb tank, and parking it next to your hookup. You need a friend to horse it there, but it may be there for a LONG time before you need to refill it.
Also: Here in Alberta, you can get an older tank recertified (Pressure test and a new valve) for much less than the new cost. Not worth it for the barbecue size but for 40's and up it may be worth it. Many propane dealers are set up to do this.
A final thought: While $5 a gallon is too much, your project is going to save you only a hundred bucks a year, and the first year of that is gone to get your tanks. Is it worth it?
Keep your tanks painted to stop rust. Either aluminum or white.
Best Answer
It's possible, but unless your furnace is way over sized, you can't just stick a heavier box in the same packaging and burn wood in it. You can reuse the duct work and blower, but everything else would need to be replaced. Depending on how much heat you need, it may not make sense to place the fire box where your furnace is. Further more, you may want to keep the propane as a back up. Don't discount how convenient it might be once in a while to turn a valve, strike a match, turn a switch and have instant heat.
Heating 100% with wood in any cold climate takes a huge volume of wood. If you don't plan for easy transport of fuel from storage into the firebox, as well as good storage convenient to vehicle access, the scheme is doomed. Because of this, many serious wood burners have a boiler system to move heat from the firebox to the air handling unit (or directly to radiators). It's much easier to move heat stored in a fluid than to lug blocks of wood through the house and up and down stairs.
Consider carefully if you're ready for this. Every part of wood burning is dirty, hard work. When you factor in all the costs and effort, propane can be a competitive alternative. Another option many people take is to leave the HVAC system and install a wood stove in the main living area at a central location. The wood stove is capable of heating much of the house. The HVAC system is used to keep the outer rooms heated. This will typically involve re-balancing the duct system and moving the thermostat.
There's a lot of different possible solutions, what's best will depend on climate, house size, lifestyle, personal habits and preferences, etc. Locate contractors that specialize in wood fired heating systems, not just simple stove installations. It takes someone with that experience to make a reasonable recommendation based on your particular situation.