You can use nylon or steel stand-offs, if in doubt it’s safest to stick with nylon. The PCB holes for the stand-offs are not connected to the circuit ground, so this won’t make any difference to your star grounding point.
16V-------> AC30
0----------> CT
16V-------> AC30
If XLR pin 1 is the shield, the chassis should act as an extension of that shield, the best way to do this is to connect pin 1 via the shortest wire at the entry point of the chassis. This is all explained in rane notes.