"Good and evil may not be out there in the world, but they must have existed as potentialities/tendencies before the Fall."

This is exactly the crux of it. Good and evil are illusions, they don't exist as potentialities. What exists are potential outcomes or consequences based in causality. The categories of good and evil are then merely human euphemisms for likes and dislikes of those outcomes.

"how, for example, does one integrate the aggressive impulses, immoral urges, and unacceptable sexual desires mentioned in the article?"

By accepting them as part of the package. Aggression used “properly” is simply assertiveness and without sexual desires, humanity would go extinct within a single generation. None of those impulses are good or bad per-se. They get twisted by nurture.

"You don't recommend trying to integrate a pure evil archetype, but suppose that were necessary?"

Another good question. Of course in the end it is necessary to integrate the Devil. But –

Well, it should be understood,
there's no evil, there's no good.
Love the Devil as your brother,
God will bless you like no other.

In other words, “love your enemies”. Better yet, allow even the undesirable consequences to be – allow the pest to be a pest. That, of course, does not preclude using pest control measures. As for Faust, he simply tried to use the obvious moral ambiguity (or absence of objective good and evil) to excuse his motivation based in his burning desire — “if there’s no objective good and evil, anything goes no matter the consequences.” Hence, his downfall.

You've already seen this article, but anyway:

https://senderspike.medium.com/the-problem-of-evil-569af1681d97