* The crafty beast had already fallen before he began working to trip up Adam and Eve.
* Adam and Eve arrived on earth as two adults, previously educated. They spoke the same language as the beast.
* Life had already evolved on this old earth; Cain and Able made contributions to a religious order. "Flocks" and "fields"???? There were many more people than just Adams family.
* After killing his brother, Cain decided to leave his parents, he fears tribes out in the world. God even agrees, puts a "mark" on him. Cain finds a wife among the Nodites.
* Imperfection of Gods children may be inevitable, but Sin is a choice.
That Satan rebelled earlier and then deceived Eve is not an issue. God created him earlier, too, since the angels watched as God created the world and they rejoiced (Job 38:4-7).
Adam and Eve arrived as adults who were highly intelligent. Whatever they didn't know inherently (from God placing the knowledge in them), they could ask God about. There's nothing about evolution in this. God made His creation very good from the beginning.
Your statement, "Life had already evolved on this old earth; Cain and Able made contributions to a religious order" has no basis in reality. The flocks (which they were not permitted to eat) were likely due to God requiring blood sacrifices for sin (Genesis 3:21), their need for clothing, and the use of animals for farming. Or, who knows, maybe God permitted them to drink the milk. However, eating animals was not allowed until after the flood (Genesis 9:3). Abel's offering of a blood sacrifice was accepted. Cain's offering of plants was not. God asked Cain to offer blood likewise.
Adam and Eve would have had multiple children and they would have had children. There's no person outside of Adam's race--even Eve descended from Adam through his rib. We don't know how old Cain was when he killed Abel. Most likely, Cain married his sister. The implication from the way he is named is that Cain was the firstborn son of Adam and Eve. All of Adam's and Eve's sons had to marry their sisters (or nieces, etc.). The prohibition to marry sisters didn't happen until Moses, which was quite a long time later (after the gene pool degraded for awhile). Adam and Eve and their children had perhaps multiplied widely before Cain murdered Abel and was banished. That's probably why he asks for this protection.
Imperfection and sin is a result of Adam's sin, not God's creating ability or method. You have no authority to say anything else.
* Paul never knew Jesus, he never heard Jesus preach the original gospel, he brought his own Pagan beliefs to the remixed gospel that emerged after the cross. Paul and others are simply wrong to speculate that one man brought Sin into the world. Besides, to follow the story as it is written in the Bible it's more accurate to say "one fallen angel" brought sin into the world.
Paul lived at the same time as Jesus (so he would not have been ignorant of Jesus' ministry), he met Him on the road to Damascus (Acts 9), and He revealed the gospel to Paul (Galatians 1:12), which was confirmed many years later by the the other apostles in Jerusalem (Galatians 1:16-2:9). His letters were affirmed as Scripture by Peter (2 Peter 3:15-16) when he refers to people's abuse of Paul's letters and "the other Scriptures". Paul bashing is a violation of this forum.
Adam was the federal head of the human race so when he sinned, he brought sin on the entire human race. Satan's rebellion was inconsequential to the spiritual condition of man.