You are right that there is no specific talk of bad conduct and no specific talk of a bad sacrifice. I was just saying that the text gives more specific evidence of an insufficient sacrifice. That is the only comparative difference that's noted in the text. "But Abel brought fat portions from the firstborn of his flock." The rest of the OT shows that meat sacrifices were more valuable than non-meat, fatty meat was more valuable than non-fatty, and firstborn were more valuable than non-firstborn. Still, there's not a lot to go on, and maybe the first audience saw something else that we can't. I also agree that a story like this begs for some further explanation like the one you give it. And that's also the mark of several of the small but powerful "morality play" stories that survive from ancient cultures.
The real differences in the way you read it and the way I read it is that issue of reading the Bible as one great story. You admit that you do, and admit that I no longer do. I am still very interested in what the Bible means, what it meant to the audience, what the writer meant, why it was kept and later called inspired (and why some other parts were kept and were not later called inspired).
As just a minor example of why I see the Bible as a collection of potentially disjointed stories is exemplified by the fact that (coincidentally) two New Testament writers seemed to have the same two differing viewpoints that we are discussing. The writer of Hebrews sees Cain as having an insufficient sacrifice. Yet, the writer of First John sees him as having an insufficient way of living.
By faith Abel offered God a better sacrifice than Cain did. By faith he was commended as a righteous man, when God spoke well of his offerings. And by faith he still speaks, even though he is dead.
1 John 3:12
Do not be like Cain, who belonged to the evil one and murdered his brother. And why did he murder him? Because his own actions were evil and his brother's were righteous.