"...knowing the composition isn't required for knowing something exists" has to do with observed effects. Yet, you don't hold God to the same standard!
Of course I do! I hold the hypothesis of God to *exactly* the same standards.
What actual, testable predictions has the hypothesis of God produced?
What mathematical theory describes the interaction of God with matter?
What alternative explanations have been proposed, tested, and rejected because of the evidence?
What theoretical proposals are there for the composition of God that can be tested (if not with current technology)?
What sort of evidence would show that the God hypothesis is invalid?
The Dark matter hypothesis passes ALL of these tests easily. The God hypothesis passes NONE of them.
So, yes, I hold the God hypothesis to the exact same standards I do any other hypothesis. And it fails miserably when evaluated by those standards.