Not an expert here, but the lack of timing at the cam (timing marks) can and normally do effect both cranking compression and vacuum. This by your description is an obvious issue. New timing chain in order here. And as long as you are there, degree the cam. After reviewing the lobes(be very aware of a non-normal wear patern) check the lifter bottoms. Answer that "cam issue" question for yourself. Ultimate cam timing does effect everything from idle to mid range in a large way....maybe not so much at the top end.
This is an excellent thread for all of us...but not necessarily you. Lots of ideas....but thats what you want. Cure the known issue and let us know the results. By the responses, you've got alot of interest and help here.