Let start at the beginning. You say:
We see time as an illusion, but God sees reality as a Big Now, all exists at once. Since God created all, he created all at once. It follows then that there is no temporal cause and effect, A does not cause B which Causes C. The only connection between A, B, and C is God's creation of them as they are.
Everything that exists is similarly existent because God creates every fact of the Universe in "time" knowingly and personally.
That God creates objects (and their effects) is not obviously incompatible with causes genuinely bringing about their effects. Thomas Aquinas, for example, thought that when God created objects he also created their causal powers. He would say, I think, that it is no more impossible for God to give a baseball the power to break a window upon impact than it is for him to make it round, or white, or of a certain size. Granted, if it is thrown at a window and it breaks, God created the event of the window's breaking, and so caused it in one sense, but so did the ball, in a different sense.
Some Thomists have made this kind of an analogy: If Conan Doyle had written "Sherlock Holmes threw a ball at a window and it shattered" in one of his mysteries, then it would be true according to that story that a ball broke the window. Now, there is a sense in which Conan Doyle caused the window to shatter "in the world of the story" since that's how he wrote it. Still, in an important sense he did not, for what he wrote was that *Sherlock Holmes* threw the ball, not that he did--Conan Doyle didn't write himself into the story as one of the characters. So when we ask about what the reasons for certain fictional events are *according to a story*, we shouldn't bring in real causes. In the case of God and the universe, things are similar accordding to such Thomists, except that our creations are fictions, while God's are real things. So God creates both the ball and the window, but also the ball's *causal power*, which is exercised when God creates the event of the ball's hitting the window and thereby *causing* it to break.