Timtofly, most of the time I'm happy you're around, because you often provide a point of view that doesn't fall into the usual "camps", which I think is great. But at other times you're just terribly incoherent
Theist = someone who knows there is a God.
Christian = someones who knows there is a Jesus.
Agnostic = those who think either can be known, but has no knowledge.
Atheist = knows there is no God.
I don't know if you consider these rigorous definitions or only shorthand explanations, but they don't work as the former.
I'm not sure how to address the rest of your post, because frankly it contains a lot of sophistry. I think the important distinction we have to make is that between
fact and
belief. Beliefs don't require facts to be held. And both the agnostic/gnostic and atheist/theist terms don't deal with facts. They're used to describe persons, not the world.
Atheism/theism describes what position (you may call it belief) you hold on the question "does God exist?".
Agnosticism/gnosticism describes what position you hold on the question "can I know whether God exists?" It does
not mean "can you know anything?" (so claiming an agnostic can't know anything is absurd).
Personally, I don't think you can know whether God exists. I also think God doesn't exist. One doesn't follow from the other, at least not directly.
Among the people who believe in God, there are both those that think they can achieve certainty about his existence (in the form of divine experience, for example) and those who think they can't (but still believe, I already cited Pascal's wager as an extreme example of this).
Long story short: both are different categories in which the positions are independent of each other.
I do have one question though: Is "knowing a fact" the same as "believing a theory"?
This reeks of polemic so I'm a little cautious here: what does "believing a theory" mean to you?
In a scientific context, a theory is predictive and falsifiable description of phenomena. "Belief" doesn't exist in science, but if you mean "regard as correct", it's easy, because the answer derives directly from the definition: I regard a theory as (partially) incorrect if only one observation contradicts its predictions and thus falsifies it. Not a big deal.
Facts are, well facts. They exist objectively and either I know them or not.
I'm not sure by which relation (excuse the mathematical term) you want to compare those two statements.