One thought on holding the motor. It sounds like a lot of work. We place the engine to power stroke by watching the cam (add air slowly to see direction engine will spin) and let the engine turn til it stops. The air still holds the valves up even if the piston is down.
I worry a little about the act of holding the crank bolt. I would hate to loosen it as that is what the direction of rotation would do. Its a real mess when the balancer falls off.
Bosch Master, ASE Master, L1
33 years MB technician