Well, your babbling about Gnosticism aside, the very notion of good and evil, or "dualism" if that's what you want to call it, was brought forth by God himself with the tree that he told Adam and Eve not to eat. It is a concept that can only be defined by God as he is holy, the moral absolute. The concept of evil has always existed, but the knowledge of evil did not exist as far as Adam and Eve was concerned. It wasn't called "The tree of good & evil", it was called "The tree of the KNOWLEDGE of good and evil". This is what made Adam and Eve innocent in the eyes of God, they had no concept of what sin is before they ate of it. It will be much the same way in the new heaven and earth, the key differences is that there will be no tree giving man the knowledge of good and evil and thus no sin, no Satan, and Jesus Christ will be in the picture. The prophet Isaiah made it very clear that we won't remember the evils of this world in the new creation.
1. Well, if you view church history as 'babbling', I shutter to imagine your 'trumpism' in response to science and mathematics.
2. The word 'knowing' in the context of the story of Adam and Eve means knowledge derived for experience. Adam and Eve knew evil/disobedience/broken creation in theory before they ate the fruit.
3. Dualism was the result of the Fall, not a description of the choice between eating the fruit and not eating the fruit. God wasn't offering A&E a choice between right and wrong - he was warning them not to misuse creation; specifically, the Tree in the center of the Garden. The Tree was not magic - it didn't bequeath a super power of knowing Good from evil. Adam and Eve were not issued a cape and told to use their special powers for good. The Tree earned its name - like Wyatt Earp's gun 'peacemaker' - only a fool fails to see the irony. After eating the fruit, A&E were cursed to walk through life assigning self serving opinions to everything in creation and calling it 'good' or 'evil' based on how it served them. We do the same thing. Jesus was correct when he told the pharisees that they had no idea what good is, for this very reason.
4. A&E blocked themselves from the Tree of Life (Christ) because of their newly acquired dualistic, concrete, self serving view of the world. God created clothing (ego) for them to give them a mark (like the later Mark of Cain) of their separation from God. Paul recognized this when he writes about overthrowing the Old Man, which is a call to return to a Garden relationship with God.
5. Evil is brokenness - it is a misuse of creation. Ignorance of brokenness does not erase it. Christ provides the only solution to brokenness - returning to the Garden - the will of God is for humanity to do what we were created to do, LOVE abundantly. We must shed our ego; become vulnerable and childlike, once again, in order to love.
This is the story of humanity told in Genesis