It seems to me that the first issue with this theory insofar as it supports your definition of God, is that it assumes that one explanation for the universe's existence must be the explanation for the universe's existence. Simply because the concept of God explains the universe's existence, it does not inherently grant it validity or even truth, in the same way that ancient peoples believing in Zeus explained but did not factually prove what lightning was, what caused it, or why it was. In short, simply because another explanation has not yet been determined, say, by science, does not in fact mean that such an explanation does not exist. Again, this is similar to the fact that people used to believe that diseases were non-preventable the direct result of God's wrath, all while being ignorant of germs. Simply put, the "God of the gap" idea, the concept that God is the ultimate explanatory model for a lack of another explanatory model, seems to me a deeply flawed theory. I'd love to hear your thoughts on this!