Barbara  I had some similar experiences.  I'm not sure the PI was
being "sharp" in all cases since with one grant the sponsor
(NOAA) does not allow rebudgeting IDcs they are just lost!

To try and answer your questions without repeating all your text (so
I may miss a point or two):

In cases when IDCs are lower than the original proposal / award
budget - if this is due to the PIs rebudgeting then the difference
comes first from the PI's "share" of the IDC return, then from the
Deans share (and PI has to tell their Dean why) and lastly from the
institutional share.  Also, and this isn't policy, it just usually
works this way - unless I make a point of it just about anyone who is
paid for more than 2 days effort winds up going on the payroll, so
even if the PI calls the individual a consultant, they are still paid
a wage (plus FB plus IDC).

Conversely our policy is to not charge an account more than the
budgeted IDCs, however if expenditures warrant greater IDC recovery
and there are unexpended funds left - we recover up to the
allowable before turning any $$ back.

We try to include IDCs in fixed price negotiations based on expected
salary etc and then treat this as "fixed."  The account is
charged for the original institutional and Deans shares (account
maintainence fee).

Richard

Richard H. Moore
xxxxxx@coastal.edu