The Plausibility of Grounding Moral Values in God, Question of the week by Dr. Craig

Dear Dr. Craig,
Thank you so much for your faithfulness, zeal, and integrity in serving the Lord. I'm one of the Reasonable Faith Chapter Directors, and I recently have been discussing the ontological ground of morality with the President of my university's philosophy honors society, Phi Sigma Tau.
My friend is a moral realist, but he isn't persuaded that God's nature can sufficiently constitute the Good. He's recently advocated the position of G.E. Moore, the British ethicist who held to ethical non-naturalism.
The crux of Moore's argument is that "Good" is ineffable, beyond definition. He gives the following "open-question" argument:
If God's nature is the Good, then saying "The Good is God's nature" is equivalent to saying "God's nature is God's nature", which isn't saying much.
I've proposed the following answer to define/understand what and why the Good is in God's nature, and I'd love your help and feedback.
1) Are qualities like 'compassion', 'love', 'justice' good because they are found in God's nature, or good independently of God?
2) To claim they are good independently of God is to propose Platonism.
3) Platonism fails.
4) Therefore, they are Good because they are found in God's nature.
But why should they be Good because they are found in God's nature? Put in other words, why is God's nature good?
6) That which is good is intrinsically valuable, and ought to be valued, appreciated, or pursued.
7) God is, by definition, the Greatest Possible Being.
8) The Greatest Possible Being is that which is most valuable, worthy of appreciation, and pursuit. <== This is the crucial premise.
9) Therefore,God is that which is perfectly valuable, worthy of appreciation and pursuit.
10) From (6), (7), (8), and (9), God's nature is the Good.
My question back to him: If God does not exist, what is intrinsically valuable and ought to be valued, appreciated, or pursued?
1) If God does not exist, then there is nothing transcendent in the universe.

2) Everything in the universe is fundamentally the same stuff (quarks & waves)
3) Therefore, nothing in the universe is qualitatively different from something else, and therefore does not lay claim to valuing anything more than anything else.
4) No composite thing is more valuable than anything else.
5) Everything is of the same value.
6) We ought to value everything (atoms, plants, planets, people (made of brains, carbon, etc.), volcanoes, dogs, etc.) the same.
7) It is irrational to value people more than rocks.
8) Therefore, it is not true that we ought to value people more than rocks--they're the same.
But, if we bring the GPB back into the picture, there is now something transcendent to, and greater, than everything else. This thing therefore deserves to be valued more than everything else. And once again we have a grounding for valuing things in accordance with God (such as love, compassion, etc.) more than other things.
I'll actually be debating this person on campus in about a month's time, and so would love your help on this.
Thank you again Dr. Craig. You're an inspiration to me for the need and example of Godly Christian scholars.
Click HERE to read Dr. Craig's answer