One issue was the screw terminals were designed for much bigger wires than were on the buttons/stick. I got around this by folding the stripped part over the insulation, and putting that into the screw terminal.
If I had to do it again, I would consider something other than RJ-45. Making all the cables was a pain. Most of the controller cables I was working with had wires too big to fit into the RJ-45 connectior. I had to carefully shave the ends of the wires with a razor.
If anyone is interested in the PS2 PCB, I'll send it to you, I used the cable, but have no use for the PCB.