I don't know what an Axiom display looks like -are the sending units compatable with the VX?

If you got it to work, it should be as simple as finding the switched/dimmer controlled wire to add lights.
The GRN/RED wire at Pin 1 of the taillight relay is your dash light wire. It comes alive when the combination switch is turned to ON.

Try following the traces from a light socket on the Axiom dash cluster to find the pin/point where the Ax receives its 12V source.

If you actually got it to work, all you need to do is put a jumper in from the taillight relay to the display's connector at the appropriate place.

Can you take pics?