1) The potentiometers (pots for short) have 3 pins. The 2 outside pins are the ends of the pot, and the pin in the middle os the wiper. One of the outside pins on each pot goes to ground, the wiper of the 100 also goes to ground , and the remaining pin of the 100 goes to pin 16 of the LCD. This controls the brightness of the backlight. The wiper of the 10K goes to pin 3 of the LCD, for the contrast, and the remaining pin of the 10K goes to +5V. The wiring diagram appears correct.
2)MPXF has a file called MPXFLCD.CFG. In the section labeled [LCD Settings], change the lines for LCD=,LCDLines=, and LCDLength= to
Also in MPXPLAY.INI you need to make sure this line reads:
LCDlines =0 ;modify this to enable LCD (1 or 2)
This prevents MPXPLAY from displaying. If the LCD is enabled in both MPXF and MPXPLAY, it will not work correctly.
3) You should be able to use a parallel port extension cable.