I think you've missed Nuggin's point.
(1) A thing of certain complexity cannot create another thing that is more complex than itself.
No, his argument doesn't depend on that, just on the proposition that anything that designed life on Earth must be more complex than, for example, a prokaryote.
(2) The designer IDists are referring to started out as less complex than the least complex life on earth and remained less complex than the least complex life on earth.
Not necessarily. But if IDists were to claim that started out simple and evolved to become more complex --- complex enough to design life on Earth --- then his point is that then the IDists have practically given the whole show away, since they have always claimed that the creation of ordered complexity is exactly the sort of thing which needs a designer and which cannot evolve. To maintain that the designer itself evolved is to admit that a designer is not necessary (and that evolution is sufficient) to explain the very phenomenon for which ID purports to provide an explanation.
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