You need to change your homez.g and homeall.g files to use an endstop switch instead of a Z probe. see https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Homing_Z.
It sounds like your Z steps/mm is set much too low in the M92 command. Also you are using x128 ,microstepping on all axes, andf while you might get away with it on X and Y, if the Z axis is leadscrew-driven then you will probably need to use lower microstepping to keep the step rate reasonable.
Again, if your Z axis is leadscrew-driven, then you need a much lower Z max speed than 12000 in your M203 command, and a much lower Z jerk in the M566 command.
HTH David