Atheism, Agnosticism, Theism

I often find myself torn on where I draw the lines between these groups. Each one of them carries a certain stereotype, and I have discovered that I don't really fit any of them. In doing so, I have come to the conclusion that I must be a hybrid of two, seeing as how Atheism and Theism are polar and Agnosticism an attempt to find a middle stance. Now, I easily don't fit in Theism, because I don't believe that any of the established religions on Earth are convincing enough to make me follow them; in fact, their very plurality and universality question their probability. For a long time, I believed that I fit in the category of Atheism, only because it was the other choice: the denial of all possibilities presented by Theism. To avoid a paradoxical argument, however, I now realize that I cannot say that I am a full Atheist. To deny the chance that a single religion could be right would be to ignore my core belief that the universe is infinite, and within infinity, anything can and will eventually happen. Therefore, a complete and outright denial of any particular religion is not genuine, rather, I have to phrase it to mean that I find it highly improbable that we have already conceived of the absolute divine truth. On the Richard Dawkins Scale, I would have to place myself as a 6, finding either 1 or 7 to be saying more than is provable and, honestly, outlandish and close-minded. So this middle ground, which Dawkins calls a "De-Facto Atheist", is where I fit; a slightly agnostic atheist. So I view the world as more of a naturalist and a scientist, finding psychological and emotional ways to feel spiritually individual, and believing that anyone who boasts to know the truth about God, whether that he definitely exists or definitely does not exist, isn't going to be showing conclusive, concrete, convincing evidence anytime soon.

Is it responsible to trust someone who claims that they know for sure something that is unprovable, or does a person's religious convictions vary enough from their day-to-day beliefs to make that a harsh judgment?