That said, my questions stand:
"That * was exactly my point, so still, isn’t the obvious equivalent [to Darwin’s criterion]: “If it could be demonstrated that it is not true for any of the complex organs which exist that they could not possibly have been formed by numerous, successive, slight modifications, ID theory would absolutely break down”?*
This is not a good falsifiability test since it requires complete knowledge. Darwin’s test does not require complete knowledge, just a single example. ID needs a falsifiability test that can be met with a single, or a few, examples. ID cannot just set itself up as the default, which is what a complete knowledge falsifiability criterion does. The default in science is “we don’t know”. Had Behe’s IC proved to be the barrier to evolution that he had hoped then the scientific consensus would be “we don’t know how the bacterial flagellum originated”. In order to move from there to “the bacterial flagellum was designed” the ID side would need to get specific on where, when, how, by whom it was designed.