As you say we can neither prove nor disprove the account scientifically making science irrelevant to your analysis of the credibility of the story.
The Bible is both a historical and a Divinely inspired manuscript. It was written down by historical figures like Moses in this case on the back of a very long oral tradition and describes literal-historical events. It differs from the metaphorical approach of non-Abrahamic religions in this respect.
Adam and Eve had other children. Cain also had other children, there may have been some interbreeding between the two lines though we do not know for sure. The loss of Abel would not figure in the genetic record as he would never appear in it. The genetic code and environment were not as broken as they are now in the pre-flood world making analysis based on today's conclusions dubious.
The murder is given a motive, Cain was angry that his offering was rejected and Abels accepted. The murder took place in a field. The murderer was Cain and the victim was Abel. The Bible then describes the consequences for Cain and his descendants. Sounds historical to me, though it is by no means an exhaustive report in the sense that you mean it.
Actually...you cannot prove anything
is " divinely inspired" or in any way supernatural.
It can only be taken on faith. For lo, with
proof, you have no faith; and there is no
proof.
However, there is abundant disproof of
the accuracy / hisroricity of many parts of
the bible, if read literally.
That some things ( egypt, for example)
is real says nothing for fanciful interpretation
of certain parts.
If you think otherwise, remrmber con men
always mix in some clear facts.
Your construct of reality falls apart like a
Jenga stack when a critical piece is
removed. God will be fine of course.
Whatever He may be, its not ignorance and absurdity.
A gut level comprehension of that may explain
your extreme relectance to face " flood" facts.