I'm not a bible expert, but I seem to remember that Abel became a shepherd of a flock, while Cain cultivated the land. I don't think that it's too much of a stretch to assume that the flock was used for food, and also for offerings to the Lord.
Yep. That is too much of a stretch, IMHO. That is not what the context calls for. There was no death before Adam's disobedience. By man came death, not vice versa.
Mankind was not eating flesh meat until after the flood they survived. That has been in force since then. From Adam's sin, up through Noah's time, people became a little more careful about what they were eating.
No sin was forgiven without a blood sacrifice. Obviously, Elohim did not accept vegetables as a substitute. The blood covered their sins, and the sheep skins covered their bodies as clothing.
But when the Messiah's earthly kingdom is established, the original practices will be reinstituted. See Isaiah 65:18-25.
But you see how the concept of theistic evolution turns a blind eye to these impossible contradictions, and is not a workable solution.