I believe that you correctly describe Behe's thesis. He is not saying
that the Designer creates complexity anew in every organism, but that the
DNA instructions for the construction of those IC structures must have
been the work of the IDer. His definition of IC - any combination of
parts that must work in perfect harmony to accomplish anything implies to
him that no simpler precursor could ever have existed. He has come under
much criticism for his postulate that no step-by-step explanation has or
can ever be found for any of these systems.
One interesting counter-illustration that I read (but not sure where, I
think in PSCF) is to imagine a stone arch - it could never have formed by
simple addition of those stone that we see now - it would always fall
down part way through. What the observer doesn't see are the
surrounding skeletal structure the workmen used during construction
because its long gone now.
Behe accepts the antiquity of the earth, and a form of common descent. I
am not sure whether he believes that all the instructions for all living
things were planted in that first created organism, or whether new
information was added sporadically over time. Glen Morton has questioned
mathematically whether all the information for all living things could
have possibly been hidden in that first cell's DNA. The second option.
occasional creative actions, looks like the Progressive Creationist's
reaction to the "sudden" appearance of forms in the fossil record. Hugh
Ross (Reasons to Believe) pretty much adopts this position.
Just some thoughts.