The axis travels seem to match commands, so it is on to the spindle. After searching this thread and looking at the M3 spindle config, I tried the following.
Set output signals 5-7 as spindle freg, spindle fwd, spindle rev, pins 14, 2, 4 respectively. Set frequency to 1800 on pin 14. FWIW, it seems that output signals 1-4 have charge pump locked as their name, and any names specified for others are not saved to the profile until M4 is stopped and restarted.
Set the input signals for Spindle On, Spindle Fwd, and Spindle Rev to device Darwin and the respective signals.
However spindle does not turn on. History states that Signal 5 turns ion and off.