I cannot recommend using that new spindle with the VFD that you have. The limited frequency range I can handle (it just means a lower maximum RPM - 18k RPM), but the lower power drive means that you carry significant risk of damaging the VFD.

There are settable parameters on the VFD that allow you to set motor current - but my feeling is that these are used to trigger the over-current protection, not to limit the motor current.

The problem now is that you've sourced the spindle - the supplier may be reluctant to support any subsequent change.

...unless anyone else knows more about the VFD motor-current settings?