If Adam and Eve had not eaten of the Tree, they would never have sinned, and neither would we. The Angels do not sin. A plant does not sin. Sinlessness is the natural property of creatures as well as Creator. By itself it doesn't indicate divinity.
Now, on Abel and Enoch, you're right. There is no explicit testimony that they sinned. So if we are holding to the principle of "Sola Scriptura", we must be appropriately cautious and say, simply, "we aren't sure." Maybe they sinned, maybe they didn't. Scripture doesn't say either way.
Of what kind of Tree did they eat? Was it a mythical tree, a literal tree, or an imaginary tree? I think it is necessary to know what the sin was if I am going to be required to be held to account for that original sin?
When did Lucifer fall? Was it before the Garden of Eden or after? Seems to me that for there to be a tree of the knowledge of good and evil planted in the garden along side the Tree of Life, before Eve was created, some action had already taken place. Eve is called the mother of all living... and she most definitely sinned, so is that a problem for that Christ was to come out of her descendants?
What does the word angel literally mean? Because I do not agree that Angels do not sin. There are good angels and evil angels.
I do not understand why so much effort and energy is invested in the art of perfecting Mary, when it does in fact take so much effort and energy. There is nothing any of us living in these flesh bodies today can do to change anything that has gone before us. Perfecting Mary has nothing to do with what is to come in future days.