That's cool you got a thermostat in there, and got some heat going. Since your heater fan works on other speeds, my first thought on that would be a broken resistor, or maybe the switch has a bad position.
Jeremiah said he saw you on the freeway the other day with rain pouring down. Do your wipers work? Looking good keep it up.
btw, I think you should get some more stuff working on that thing before you take you wife for any more rides :D