Sorry for butting into your interesting conversation with Benjamin, but the whole christian atonement theology and all questions associated with it are based on a false premise — Jesus died because of our sins (not for as in substitute). This can be clearly seen when one looks at original verses in Hebrew Tanakh. It’s also quite common sense.

Wounded Because of Our Sins

As for Gnosticism vs Orthodoxy — I think it’s invaluable to look into Irenaeus.

Against Heresies and Irenaeus