All of this "God is truthfulness" and "God defines (insert quality)" just sounds like total nonsense to me. How is god an abstract quality? Last time I heard the average theist talk about it, god is some sort of all-supreme, disembodied superbeing. What does "God is love" or "God is truthfullness" actually mean? It just seems like a way of avoiding the unsavory implications of divine command theory. Saying that moral absolutes are just "God's nature" just pushes the problem back one step. Why is God's nature a particular way? Could it have been different? Is his nature the result of some logical rule? Can he decide his nature? (Lots of God's free will, eternal, omnipotent incoherence problems with this type of theism.) All of this is hand-waving.
Extra credit: Does god need to exist for mathematical statements true? Just as you claim that there needs to be a divine lawgiver for morality to exists, does there have to be a cosmic mathematician for 1+1=2?
"In the meantime, you can live off our (unexplainable to you) morality until you manage to figure out something better"
Who, exactly is the "our" in this sentence? Are you part of a group of roving moral philosophers? Surely you can't be talking about some mythical "Judeo-Christian ethic" which has, in reality, been shaped by many forces in society and definitely improved (according to most people) over time.