I'm not a christian, but I grew up in a Baptist household, so I have at least a passing understanding of the Bible. Lemme know if I got any wrong.
If I'm understanding the bible correctly;
God Created heaven and Earth, Including Mankind and Angels
God is all-knowing and all-powerful
Relevant to this discussion, God created Lucifer and all the angels who sided with him.
God made Man in His image, and ordered the angels to serve them.
Lucifer, prideful of his own beauty, and envious of God's (at least perceived) favoritism of Man, and of God's position, started a rebellion in heaven and was/will be cast down into the lake of fire(aka Hell).
lucifer later tempted/took the form of the Serpent in the Garden of Eden and tempted Eve to eat of the Tree of Knowledge.
my conclusion: God, with full knowledge of what lucifer would do/become created him and set him on the path that led to his downfall, and to the Sin of Mankind.
Or to put it more simply; God created Sin through his foreknowledge of what Lucifer would become.
I'm not trying to start a shitstorm here, but this is the logical conclusion that I find myself at.
Any Christian pedes wanna poke holes in this for me?
So, your conclusion is valid up to the point where you say God created sin. If you had said, God created evil you would be correct and I could show you ample scriptural proof.
Sin literally means, to miss the target, as in archery. You aimed for the bullseye but went off the mark.
Understanding the distinction between sin as an action that effects the force of evil versus evil's true purpose and function is a great philosophical journey.
I could give you my conclusions from having taken that journey but more wisdom is gained from you asking the correct questions and earnestly seeking out those answers for yourself.