Upgrading OZO router driller with MKS dlc32 Laser / spindle

Hello, I am new and I ask for some help .
The cnc is controlled by an OLD Pc386DX2 and an IO card. I have connected the DB25 pins to a MKS dlc 32 and the axis are moving (XYZ) but there is no feedback nor index, only flag used for autozero.
My prblem : I want to control my spindle. The tension is like in parallel connector : between 1v and 3.3V. The frequency is 0 to 1khz (100.000RPM) (very fast for pcb routing drilling) usually working at 40000 RPM. I don’t want to use 0-10V command. Is it possible to change the output to frequency?
Other question, is MKS able to do Tool changing?
I want to use the laser for engraving and the spindle to cut, the laser is mounted in an extra spindle chassis.