The OP is based on the view that God is omniscient and omnipotent, so he had the power and foreknowledge to avoid the occurrence of the original sin. That makes him complicit, and as the more powerful entity on the scene, responsible.
I don’t know why you’re talking about Cain and Able. That doesn’t really have anything to do with it.
It has to do with the question of foreknowledge and if they were pre-ordained to disobey and eat of the tree of knowledge. So, I will ask again, did God know that they ate of the tree of knowledge or would eat from in? When God asks Adam and Eve “where are you” is there any indication that he already knew where they were? When he asked: "Have you eaten from the tree that I commanded you not to eat from?” is there any indication that he already knew?
We have discussed this, but your claim that God is responsible for what man does, is just that, and not more than that, no matter how many times you repeat it.
That there is evil is certainly a problem. That there is a God who could eliminate the problem is only a problem for those who believe there is such a God and wish to maintain the belief that God is omnibenevolent in the face of evil.
The story of Job takes a middle ground. The problem is acknowledged, but the conclusion is that it is beyond our comprehension to understand why God does not do something about it.
That’s the later Problem of Evil. The old Problem of Evil has to do with the creation of evil out of a single, unified Creator. The OP is a version of that.