Don't know what version of the CNCusb you tried but it is a nice layout and very usefull. Unless you just HAVE to have gameboy graphics on your screen you should give it a try . Their software is capable of things that MAch3 can only dream of having at this point in time.
A far as I know the CNCusb will never run on mach3, without someone creating a Plugin and I really see no reason to.
IF you need HELP with the pendant I suggest you contact PlanetCNC (;-) THEY are your best option at this point.
(;-) TP