If you put the motor valve after any other valve with PB and you operate that valve it will reduce flow to the last valve or to the motor as it will bypass fluid flow strait to the tank.
Are all the in and out ports the same size?
I personally would only use the PTO pump for the motor circuit and use the Tractor pump for the controls, that way as you move the unit you will not reduce the flow and speed to the cutter head.
First Option:
PTO pump for motor
Tractor Pump for controls
Second option:
Just make a series circuit out of the whole PTO system, out of pump, to in of one valve out of that valve, to in of the next, and so on, I would make the motor valve the last, that will only work well if all the ports are the same size, also if there is any restriction on a valve, like the Joystick valve, it will restrict flow and speed to the cutter head and cause a large heat gain.
Third option:
You will need a regulated / controlled Tee valve (won't work with a normal open tee, as it would just flow to the easiest path), send one side to the control valves and the other side to the motor valve.