An actual reply: The question "How did the universe arise?" is equivalent to "How did God arise?". You do not have to explain how the universe came into existence in order to accept that the universe exists, and the same applies to God.

Your main point in your reply is that God fails occam's razor. He does not help us understand the universe nor the physical phenomena; He is just a less embarrassing replacement of the word magic. God has poor explanatory power, and this is a good argument.

If from the beginning you do not accept that God is a good explanation for our existence, you do not have to play the theist's game. If you do, then you cannot afterwards tell the theist to provide an explanation for his God or you won't believe in Him, because 1)this question is irrelevant as shown earlier and 2)his theology already provides an adequate answer for this question once you conceded/entertained the thought that God could provide a good explanation for our existence.