One thing!

I can't work out from the silk-screen labelling on that board which of the axis-inputs are ground and which are connected to the inputs to the micro controller.

If you have a multimeter (and you really need one for this - even a cheap one from Amazon) - you need to check which 6 pins in line on the axis-limits inputs are all connected together - these are the ground returns. For the remaining 6 pins, I expect each pair, for X/Y/Z to be shorted together - these are what you connect the resistors to.