In order to get the prescribed 12 BDTC advance on my 88 760 turbo, the distributor needs to be rotated cw tight against the bolts. I double checked the timing belt marks and they appear to be aligned ok.
Is there anything on this car that would affect the timing?

The timing mark is on the outer ring of the harmonic balancer/combined with the crankshaft vbelt pulley. If the outer ring moves relative t¿ the center ring (the elastomer ring between the two is yielding or the bond is failing) the  iming mark will be off and/or impossible to find or maintain.

Scribe ¿r paint a white line across the elastomer ring so you can see if the line is broken after a few days or even when you rev the engine a bit. If so, replace the balancer. Not unusual to replace them every ten years or so...I went through a couple in 150K miles on the 87 760T.

Have you moved the distributor CCW, and has this resulted in less advance? I was under the impression that rotating the distributor within the elongated bolt holes would have no effect on timing either way. Thanks!!

The knock sensor affects the timeing by adjusting for knock. doesnt actually adjust the timeing itself but will affect it.