"why would God in all of his wisdom and love and justice punish his own perfect son for the sins of his other imperfect creation?"
This is for many reasons. His son was a willing sacrifice because He loves us and this had to be done to make intercession with the father. There were also many prophecies about this that had to be fulfilled to complete God's word. Jesus also died to bring to an end the 'law' of the old testament or first covenant and bring about the mercy and grace of the 2nd covenant.
"How would this punishment of the innocent logically bring about salvation to the guilty?"
Only perfect, innocent-as you say-blood, can be shed for sin. Jesus was perfect and did no wrong. He was the only one throughout history that could have done this for us because he was completely filled with the holy spirit of God.
This link may help for first 2 questions:
"Why would a perfect God create something imperfect knowing that in the end many of the imperfect ones would fail to "believe" and then torture or banish them forever for it?"
Good question. One that I have struggled with before. The best answer that I can give you is that God is glorified when we use our free will to choose Him over something else that may bring us momentary pleasure. God always wants us to choose Him and our relationship with Him first and its very difficult. If God had not allowed sin to happen then there would be no free will. There is no freedom and liberty without the opposite-tyranny. We choose freedom or tyranny theologically as we also do politically.
"Why would God in all of his justice and wisdom offer bribes and punishments based on ability to believe rather than on the measure of goodness and evil in each individual?"
First it isn't a bride-salvation is a free gift from a loving God. Why does He even love us to begin with? I don't even know. We are all evil. 2nd, we all have the ability to believe. 3rd, We cannot save our own souls because we are not inherently holy. We need Jesus to be washed clean and forgiven for our sins. Our good works are but meaningless, filthy rags until we are saved and accept Christ.
But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.
And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more.