Aside from cleaning the bugs out of the mesh, the best thing for my heating (besides turning on the A/C to light off the second fan) was Marc H's chip. Among other things, turns both fans on at (I forget exactly) around 210 and shuts them both off at 205(?)). Since then my gauge never wanders above mid scale in normal stop n go or highway driving.
As for the miracle additives for your coolant, you'll find them right next to the "Tornadoes" for your throttle body there at Wallyworld.
P.