You are correct in thinking that a large stator will give you more output at low windspeeds.
A large stator increases the velocity of the magnets over the coils. This increases the output.
You must have enough torque to move the large stator.
That means you must have POWER.
If you build a large stator, you will need a large prop.
http://www.otherpower.com/bigmills2.html
Look at the 14 foot mill on otherpower.
The large stator stalled the prop until the airgap was increased to 1 inch.
If the same rotor was on a 20 foot mill and the airgap was narrowed to 1/8 on an inch, it would really be impressive.
There is no advantage in storing heat in another medium and then transferring it to water. Every extra step adds cost. Water sucks up tremendous heat and is a good storage medium in itself. Just insulate your tank.
You don't need to double or triple your coils. Just use a bigger, stronger magnet.
When you consider the cost of your tower, the work to build the blades and the wire and epoxy, the cost of another $100 to buy the mother of all magnets will be a bargain.
Wind coils big enough to span the full magnet length and width.
Hot water heating elements are usually 110 volts or 220 volts.
They run on DC just as well as AC.
High voltage coils use smaller wire, drop less in resistance losses and it costs less to get it to your house.
You must increase the voltage to run your heating elements.
Higher voltage coils will reduce the amount you have to boost your output to match your heater.
Hot water heat is "low quality" power" You may be able to get much cheaper hot water by building a solar collector. They are very low tech, reliable and they work.
Keep your electricity for lights, and quality power use through an inverter.
You will get much better value for your work by replacing your 110 volt loads.
Propane will give you fast, easy hot water if you need it. And the propane will wait in the bottle till you need it, not like wind.