I agree with much of what you say, but I’m not sure you define “good” and “evil.” Do you believe that they are working together in this world?
To say that we experience them both because of the fall is true, but how? For example, at least some Jews believe that we have two minds, one from the divine soul and the other from the animal soul. This may or may not be correct, but it does better job at explaining them than most of the other posts on this thread. (If we have two largely independent brains, one male and the other female, it stands to reason that we have two minds.)
The Church teaches that we have two minds in a sense. One is led by the spirit and reason, drawn to delighting in righteousness and obedience, while the other doesn’t really care about anything except what it can get, what might benefit it or give it pleasure, etc. That side only
wants; it doesn’t know what it wants for sure but is persuaded that, unless it continues to want, it won’t
have, it won’t have all that it
could have, or be all that it could be.
That is the state or attitude or persuasion or concept initiated by Adam, requiring a breech from his Creator. It’s essence, in fact, is lack of trust in God, that God will satisfy us. Once we lose trust in God, we
have no God for all practical purposes; we become our
own god. But, as Jesus tells us, “apart from Me you can do nothing.” And Aquinas: “God, alone, satisfies.” We’re here, with the opportunities we have which include the knowledge of good and evil, to learn those lessons: God exists and He is trustworthy and true and man needs Him; man was
made for communion with God. At some point, in full communion, we will have all we can possibly want.
Evil, in one sense, is anything less than full communion with God. The worst evil we now experience is a sort of semi-detachment from Him in our exile here, even as belivers. Again, anything that detracts from or takes away from the perfection that otherwise issues from God, is evil to one degree or another, even if only slightly, relative to the perfect good He has in mind.
But as all perfection depends on and comes from Him, it lies in being aligned with Him and His will. Anything outside of that tends towards chaos , disorder, injustice: evil- the evil that we all know here in a million different ways. To the extent that we’re in union with God we acheive our own perfection.
In this life were asked to walk by faith-faith, itself, being a relatively dim foretaste of that union, of the “vision” of God. But here we’re challenged to seek it, to develop a hunger for it, to come to want only Him, the ultimate Good, above all else, to turn from the evil we know here, to begin on the road to perfection that finally is consummated in complete Union with Him in the hereafter.