Is the machine calibrated, so requesting 10mm moves 10mm etc? Sort this first. This is set with the 'steps per' box in the motor tuning and can be worked out from the stepper motor, thread pitch etc., or at least estimated by trial and error to get you going. Use the MDI box to ask for 100mm movement, and then measure how far it actually goes. Change this 'steps per' value until it is accurate.

Once set don't use this to change the speed. Instead, alter the values in the 'velocity' box in the motor tuning section. This sets the max feedrate when jogging. I assume your 133.3333 are the jog speeds?

But when actually cutting the gcode itself will contain the feedrate to use. Press the 'gcode edit' button in Mach3 and look for F500 or similar. Do a 'find and replace' to change this value to something quicker, but increment slowly. This rate is set when you (or whoever gave it to you) created the gcode.

It would be worth reading up on the basic Gcode commands (G0, G1 etc), so you can understand a bit more about it.

Your last sentence sounds like a multiple pass, which is quite normal for cutting thicker materials etc.

Does this help?

Barry