The RC combination in reset pin is meant to give it a power on reset pulse when power is applied. The capacitor slowly charges through the resistor keeping the module in reset for a little while.
EDIT:
For the above explanation I was thinking of the circuit without the reset switch so that's why I was talking about power on reset only. The same thing happens when the reset switch is in the circuit but now if you push the reset switch you short the capacitor to ground and puts the controller in reset and when the button comes up the capacitor starts charging again and gives the small delay until the reset pin is at high level again and the controller comes out of reset. So reset switch just allows you to reset it when you want.
You need to have the FS set to same setting as in software. So if you set the FS to 8 pixel wide setting then the software has to be set to 8 pixel font too. And same for 6 pixel. If this hardware setting doesn't match the software settings you get some interesting results. I don't know of software that would support changing the hardware font setting through parallel port pin or something though.
But yes you if you make some arrangements so that you can change the pin between high and low with a switch you can make some experiments. LCDInfo supports both 6 and 8 pixel wide characters.
Yes you can test the negative voltage output by just connecting the
2. VSS (Ground)
3. VDD (5.0v Supply)
and then checking the output from Vout.
Sure you can program plugins for LCDInfo

The information and files needed are in the
Developers forum but if you run into some troubles or don't understand something just ask.