I had understood the author to be referring to the Supreme Court alone, but I accept your proposition that "unqualified" was referring justifiably to the lower courts ("ill-gotten" seems wrong in any case).

Further, I concede that I should have written "tend to vote in lock-step". Thanks for the correction. For the numbers I refer you to Ilya Shapiro's article https://www.usatoday.com/story/opinion/2019/09/10/liberal-supreme-court-justices-vote-in-lockstep-not-the-conservative-justices-column/2028450001/. I'm no kind of expert on this, but I assume he is, and anyway the raw data is available.

Your final paragraph is eminently reasonable, but given that the author wrote "If the Court makes it impossible to provide universal health care, to deal effectively with climate change, and to reduce social and economic inequalities, then—and only then—expand the number of justices to eleven," I can't square what you wrote with what he wrote. He's talking about outcomes, not jurisprudence. I suppose you can argue that "makes it impossible" means that the conservatives vote for certain outcomes regardless of the law or the facts, but I don't take that to be the plain meaning.