There's a 4th IP bolt at the tail end of the IP. Loosen the horizontal bolt (13mm wrench) into the IP, not the two bolts into the block.

This is the best picture I can find of the crank pulley indicator. It's the brass thing under the water pump. This angle doesn't show the pointer that extends horizontally over the damper but you can see its shadow at about 11 o'clock from the crankshaft. You must have seen it if you saw the 10* BTDC mark.



Mind you, that bracket with pointer is adjustable. MB in its infinite wisdom decided someone ought to pull a prechamber and directly verify TDC. Why they put timing marks on rubber is beyond me.

I don't think there's enough IP timing adjustment range to restore a 35* offset. Either the chain skipped several teeth, someone didn't install the IP correctly or the timer is jammed in an advance setting. Unfortunately the advance mechanism on the hidden side of the timer so just pulling the vacuum pump isn't enough. On the other hand there's little else to do but lift the chain and remove the timer once the vacuum pump is off.

Sixto
87 300D