Yes, I still have trouble where "beyond understanding" is in (3). One reason I'm having trouble is because theologians, for example, have made arguments about ascribing various properties about the designer, e.g. that the designer is omnipotent, spaceless, timeless, etc. This shouldn't be possible even in principle if the designer is beyond understanding by definition, just like it's impossible to make coherent arguments that a triangle does not have three sides. You've suggested that it seems silly to be able to understand anything beyond the physical universe accessible to us when we don't yet have a full understanding of it, but "it seems silly" seems to be different from "it follows by definition". And in any case, the multiverse hypothesis is an attempt to understand something beyond the physical universe accessible to us, but presumably you wouldn't leverage this same objection against it.
If you really mean "beyond empirical inquiry", I would be inclined to agree, though I don't know how other explanations for the fine-tuning of the universe are better in this respect.
If you really mean "beyond empirical inquiry", I would be inclined to agree, though I don't know how other explanations for the fine-tuning of the universe are better in this respect.