Have you dealt with the vertical positioning on the plate? The plate should have a 2-3mm drop with freeplay before hitting the dist plunger (it will be significantly harder if done against fuel pressure - fuel pump by-passed - try it with fuel pressure and the engine off).
The position when it hits the plunger should be at the base of the vertical wall the plate moves against in the off position.
Bosch Master, ASE Master, L1
33 years MB technician