I think that VCR analogy has bigger problems too, not related to the Euthyphro dilemma. One problem is that it evaporates when we apply it to any kind of context or subject it to any kind of specificity. Presuming the design is the universe, what is optimal use of the universe? What does optimal use even mean when applied to the universe's constituent parts making use of the system? Isn't a parasite operating optimally when it makes use of a child's eyeball? Isn't a predator making optimal use of the universe when it hunts and kills a straggler to eat? Isn't a sociopath making optimal use of the universe when they capitalise on their situation and exploit those around them for maximum net gain? Lots of really bad things can be said to be more practical, optimal, peak performance for certain ends within the system. We're clearly no longer talking about morally good conduct when we say optimally good conduct.
Yes. You are absolutely correct. It is a problem that the Abrahamic faiths in particular face, though I'm not sure how much it affects other versions of theism. It ties into the entire idea of the purpose of creation and God's will. Everything in creation would in essence be enacting what is "good," from Satan, to the disbeliever, to the Antichrist, because they would all be acting optimally according to the fulfillment of God's plan.