Oh...so he does exist in the universe? In time?
Nope, though he may enter into the universe and break its laws at will.
That would make him a part of our universe then....
According to some on this thread, he would then be temporal and have a cause.
Nope, see above.
After giving it some real thought... I'd say that the best argument against god's existence lies in the arguments for his existence. They all either implicitly or explicitly begin with the conclusion that god exists and then they try to rationalize their way to that conclusion.
How does saying "everything that exists has a cause" and then going all the way back to God "implicitly or explicitly begin with the conclusion that god exists"? On the contrary, it sounds like you're beginning with the conclusion that God doesn't exist!
If I had to pick what I believe is the best argument against the existence of God, it would be this:
At the beginning, when God created this world, he had the choice between a nearly infinite number of possible worlds that he could have created. Instead of any number of those worlds, he chose to create this particular one. Now, that leads us to believe that there would be a world in which Adam/Eve did not eat of the tree of the knowledge of good/evil, and so on. It also leads us to believe that there is a possible world where the significant majority of individuals freely choose to obey God's commands. A perfect example would be the heavenly world where at least 2/3 of the creatures do in fact choose to obey God's commands.
The question then is: why would God freely choose to create a world where the vast majority of free creatures freely choose to disobey his commands over a world where the opposite is true? It makes it sound as though:
1) God is apathetic
2) God is ultimately responsible for whether someone obeys or disobeys him, in other words, he makes them good or evil
That, in my view, is the strongest argument against the existence of God. Obviously, it's an argument based on morality, which is what most arguments against the existence of God are. The problem of evil, in my opinion, is a strong argument against God's existence, but not as formidable as several others.