(Cary Grant voice): "Rapid City, South Dakota!"
Does that one gas station on the east side of town still have all those stuffed and mounted big game animals?
As others have said, HHO and whatnot are all snake oil--you might as well try Rocket Tabs for all the good it will do you. I would skip the propane; I don't see that paying for itself. And I wouldn't bother with Plexiglass windows--they may be lighter, but there are easier ways to lose as much weight for no cost and not have to deal with issues like weathering, scratching, and sealing. (See the Green Grand Prix modding thread for an example list).
If you're spending considerable time idling waiting for orders, and stopping with the engine off, I would look into engine insulation to retain heat in addition to more battery capacity. Specifically, (and I'm going to try this on my car) an engine "jacket" like BMW announced they would develop a few years ago and apparently never did. But,
this guy made one for his Insight :
