That big difference between the CCC's associates estimate and the later one from the feds likely results from how the CCC tends to give the greatest possible claim as to the scope of the Outfit. So I imagine that the CCC probably defined anyone who had some kind of relationship (either long-term or temporary/opportunistic - I believe the Outfit chart made by Scott Bernstein et al uses a similar loose definition of associate), while the feds were going by a much stricter standard - probably full-time active gangsters working in crews under soldiers, along with "legitimate" businessmen/politicians/union guys/etc. who actively aided and abetted the Outfit (I believe the aforementioned chart goes ahead and lists these kinds of associates as "soldiers", regardless of made status).

And as someone said, IQ tests are a horrible indicator of native intelligence; they are more a test of whether someone has received a formal education that would prepare them to do well on an IQ test. Someone who was a very sharp guy in terms of business sense and street smarts but quit school early on probably wouldn't do that great on an IQ test; they'd also probably have an indifferent half-assed approach to the test that would also give them an artificially low score.