Larry, what's all the mystery about the harmonic ballancer? Just mark it so you can put it back the way you took it off and torque the six bolts to 18.35ft.lbs. I have never had any problem with them.
Now about the piece of the plastic chain guide:if the chain tensioner failed or the sliding rail broke,that might let the chain jump a tooth at the cam sprocket and not at the crankshaft.There just isn't enough room down there. That might might explain the piece of plastic broken from the chain guide. I believe that when the chain jumped time, the number one piston has hit one of the valves bending it or both of them. That would explain the low pressure on number one cylinder You can check this by removing the number one glow plug or injector and using an adapter, blow air into it and listen at the exhaust and intakes for any air escaping.
A bent valve(s) could explain the low compression and difficulty in starting.
Do keep us posted on this. The suspense Is greater than a Hitchcock Thriller.
By the way;do you remember when the early Mercedes did not have harmonic balancers? Now they are called balancing discs.