Answers;
1) Select PoKeys pin ID from the list for the A and B channels where you have connected your MPG to.
2) No need to set anything in the Mach3 encoder settings. Leave it on default. There are no port and pins configurations in PoKeys device and no mapping to parallel port should be specified.
3) map the MPG to MPG1,2 or 3
4) From the manual:
Plugin supports the usage of pendant with activation switch. If such pendant is connected to PoKeys,
'Pendant mode' should be enabled (checkbox at the bottom of the 'PoKeys mapping' dialog). In this
mode, jog action will be deactivated when the activation switch is released and will be automatically
activated when there is a signal detected for both the axis and step selection.
This means that if you have a multiple selector switch for axis (0,X,Y,Z) and step (x1,x10,x100), jogging will be selected if you switch over to one of the axis and will be deactivated when you switch back to 0 (or pressing and depressing activation/dead-man switch).