You should be using the ZDP03A programmer - https://www.digikey.com/product-detail/en/silicon-labs/ACC-DEVPLATP03A/703-1053-ND/2139694
The other option is the Equinox family of programmers but these are quite expensive.
Details on the programming are in: https://www.silabs.com/documents/login/user-guides/INS11681-Instruction-500-Series-Z-Wave-Chip-Programming-Mode.pdf. This document has the JEDEC signature.
But you shouldn’t need to go to this level of detail. The PC programmer should do all the work for you. You do not need to alter the source code of the PC Programmer. It should remember which tab you used last and default to the 500 series the next time you open it.
I suspect you are not really “acquiring” the chip and the data looks like all FFs but really the SPI pin is just always high and has not properly gone into programming mode.
Click on Tools->Detect Target. The bottom of the window should say the Target type in socket is ZW050x.
Click on the NVR tab, then Read. You should get a block of data which should not be all FFs. If that doesn’t work, then you have a connection problem.
Make sure the MISO and MOSI pins are correct and the RESET is connected.