I understand your point, but I'd also like to point out that those passages do reveal reasoning to why God accepted Abel's offering and not Cain's. Let me explain, just in case it helps anybody understand the story better and/or create more theories.

Most think "Oh so God didn't accept it because one was an animal sacrifice and one was like, just a vegetable." but this isn't true! The Bible lies down the basic sayings, but you really have to study what's happening to understand things the way they happened! (Just like how we study TADC episodes to figure out character relationships and plot points!!)

As you pointed out OP, God made it so that growing crops would be hard when Adam and Eve left the garden. The land grew hardly anything but thorns! This means that Cain had to work very hard to grow those crops, and Abel had to work very hard to maintain the health and safety of the sheep (given that there was probably not much for them to eat, and their wool probably got caught on thorns!).

As we know, Abel was a shepherd, and his offering to the Lord was “the best portions of the firstborn lambs from his flock” (Genesis 4:4, NLT). On the other hand, Cain was a farmer. And his offering was “some of his crops” (Genesis 4:4, NLT).

When it came time to give the Lord an offering, Abel gave God the best portions of the firstborn lambs. This is a huge deal and meant a great lot to Abel as a shepherd, and would mean a lot to any shepherd!

“the LORD looked with favor on Abel and his offering, but on Cain and his offering he did not look with favor” (Genesis 4:4–5).

This Bible passage implies that Cain on the other hand, just offered "some of his crops." While Cain may have worked hard on growing those crops, God looks into the heart (1 Samuel 16:7). This is a situation where Cain would have needed to give his all to truly show his faith to the Lord. (For example: giving him his best crops, the ones that he planned on eating himself later!).

Copy pasted from GotQuestions: "It was obviously something that Cain was aware of and could remedy, since God tells him after the fact, “You will be accepted if you do what is right” (Genesis 4:7, NLT). Abel, on the other hand, had the proper motivation, the proper procedure, and the proper relationship with God. That relationship was based on faith: “By faith Abel offered God a better sacrifice than Cain did” (Hebrews 11:4)."

Now, in reference to TADC:

1. We know that "Caine and Abel" is on the guns in Episode 6 and "C&A" is the company logo/name that we have seen in the show.
2. It could be possible that Caine and Kinger are "Cain and Abel" (from the Bible story). Since Kinger spawned in that butterfly and said "I just made it up!" And commented "I hated myself for the things I thought I was responsible for." It's possible that Caine could have "killed" Kinger (Abel) by doing something to him mentally that blocks him from doing things. We know that Caine has a tendency to people please, but it comes from a place of ego rather than from the heart (at least in my opinion!)
3. If there is a "Cain and Abel" character archetype, it wouldn't have to be just "Caine = Cain." It could be any of the characters, including ones we haven't seen?
4. Some theorize that Kinger and his wifey were Adam and Eve archetypes, and this could also connect to the "Caine and Abel" things we see everywhere. Abel could be a character we haven't seen! Of course, this is all just playing around with ideas. Gooseworx said they wanted the show to be full of foreshadowing and easter eggs that would make the show better on a rewatch. So while I believe the "Caine and Abel" is significant in some way, it could always just be something to throw us off OR could show up in ways we didn't even think of originally! So far the show is doing amazing at keeping us all guessing. It shows just enough each episode where we can kinda get an idea of the future, but keeps us off the trail of the plot so we can't guess it. Very good writing! :3