Your defense of Adam is not based on the facts. In fact, Adam's sin was wilfull and he manifested no repentance for his wrongdoing. He fully knew the consequences of his sin, unlike Eve, who was deceived by Satan.(1 Timothy 2:14)
Your also are wrong in saying God was responsible for Adam's sin. That is no more true than a law against murder being responsible for a murderer killing someone.
Neither did God plan his Son's sacrifice "before he created anything at all."
Concerning Jehovah, Deuteronomy 32:4 states: "perfect is his activity, for all his ways are justice. A God of faithfulness, with whom there is no injustice; righteous and upright is he." God will never act unjustly, and his providing the ransom did lay a legal basis to forgive sins. (Romans 3:22-26)
As to God's loving provision being "absurd", the words of 1 Corinthians 1:18 come to mind: "For the speech about the torture stake is foolishness to those who are perishing, but to us who are being saved it is God's power."