Complicated quantum system = Like Unnatural objects All Natural objects must be formed and brought into existence by an Intelligent being
this is flawed because you've just made a giant leap here. It's a bold assertion.
As you highlighted, atheism is a question of belief and that's all.
agnosticism is a question of knowing. You're correct in that no atheist should boldly assert "I know there is no god," but few actually do that.
Agnostic atheists do not (and cannot) know for a certainty that there is no god, just as they can't say with certainty there's not a pink teapot orbiting the sun between earth and mars.
Its a useless endeavor to prove a negative. However, the burden of proof lies on the individual(s) making the claim. If there is insufficient evidence for that claim, his audience should not believe it until such evidence is presented. And by evidence, it must be observable, testable, measurable, repeatable and falsifiable. Science allows for those requirements; faith, religion & theology do not and never have.
your conclusion that "all natural objects must be formed and brought into existence by an intelligent being" is merely a bold assertion and does NOT stop there. WHICH "intelligent being?" Oh, gee, thanks for showing me this... I TOTALLY believe in Allah now. Or Vishnu. Or Xenu.
what--that's not the conclusion you've reached? Ok then, you have more burden of proof and you've not even gotten off the ground.
demonstrate the mechanism by which all natural objects "must be" formed by an "intelligent being." Develop a protocol by which this claim can be tested--a protocol that peers can review, repeat & critique. If they come to the same conclusion, bingo! You've just won the Nobel prize! But even THEN, you'd have gotten us no closer to virgin births, walking on water and rising from the tomb after 3 days of death.
Go back to the drawing board.