You should be able to use an emi filter on the 0-10 volt command going into the spindle controller. depending on the type they are typically CLC filters, 4.7nF to ground on both phases, a 1-10mH common mode choke and .1 to 1uf capacitors line to line.

another emi filter on the ac input.

put the two emi filters in a metal box along with the spindle driver and run a shielded cable out to the motor. ground the shield to the box and the motor.