Re: “complexity”:
The original use of “complex” to describe specified information was by Leslie Orgel in 1973. However he did not mean by it that the phenotype was complicated, but only that the sequence was long and conveyed a lot of specified information. Then ID advocates started to use Orgel’s term “specified information” and used “complex” simply to mean that there was a large amount of it, enough to make it very improbable if it was generated at random.
So the whole use of “complex” in discussions of what evolutionary processes could do was, right from the start, not discussing how complicated organisms were.
There is a separate, and vast, literature which tries to measure complexity of organisms by numbers of cell types.