You are reading New Testament revelation back into the Old tTestament, which is fair enough in terms of drawing out edifying typology. But we should not be ascribing to Old Testament characters ideas originating in New Testament revelation regarding God's secret plan of the cross and only brought to light to the church in Christ after the plan had been carried out.Cain offered to God the fruit of his labour, the fruit of the sweat of his brow, he is the father of all those who say "no but we must earn our salvation with works"
Cain did not see the necessity for death to self. For the need of miraculous forgiveness. For substitution, the transferral of his sins onto an innocent victim.
... yet he slew innocent Abel.
I agree with your typological inferences. I disagree that they account for Cain's and Abel's actions. I don't think God puppeteered Cain and Abel to behave as they did in order to create a picture of spiritual truths.
I think God selected from among freely performed actions, those actions that fit spiritual truths, and had those recorded for the benefit of generations that would follow.