All Christian biblical scholars do this! And that’s exactly what I’ve been trying to convey in this entire thread. In fact @deuteroKJ gave a little taste of that in this very thread. Read any professional scholarly commentary on Genesis (whether liberal or conservative) and you’ll see this careful, scholarly study.
Now, lay Christians who aren’t scholars can’t do this because they don’t have the skill to read Hebrew or Greek. They have to read English translations, and so must rely on pastors and teachers to guide them towards features of the text which may be missed in the English translation, including cultural context, cross-references, intertextual resonances, and so on. They might read popular-level commentaries about the passage which incorporate some of the latest professional scholarship about this but without getting into the technical details.
On the other hand, if they don’t want to do all this additional work and just want to read it as it seems to read “plainly” to them, that’s fine too, but they shouldn’t expect their interpretation to be authoritative for others.
I’m not sure what you mean. First, Christians are well aware that there are multiple authors in the Bible and that it was composed over a period of centuries, if not millennia. They freely admit differences in literary style, cultural background, theological emphasis between different biblical authors. Yes, Christians take both Genesis and Revelation as part of authoritative Scripture, but this is more of a “presupposition” (this term is also a crude one - canonical development is a complex topic and I can’t go into it here) rather than logical conclusion based on purely intellectual analysis of the text. We approach the 66 books of the Bible with the assumption that it is all God’s Word and trace the intellectual consequences of that.
Second, as I said before, even if you assume that Genesis was based on a pre-Israelite work, the Genesis story you read in the KJV has definitely been edited and reworked (by Jewish scribes, editors, and compilers of Genesis) into something which reflects Hebrew cultural and theological concepts and categories. In other words, the story of Genesis as it’s presented is already somewhat tailored to harmonize with the rest of the Hebrew Bible. This influence goes both ways: post-Genesis biblical authors (including the NT) were also well aware of Genesis and referenced it when developing their theology.
As I said, if you’re not interested in any of this theology, then you have to first do some scholarly work to identify the pre-Israelite kernel of the Genesis 2:4-4:26 story. There is no way you can accomplish your goals with just analyzing an English translation of the Masoretic text, period.