When I talk about God's plan being fixed under predestination, what I mean is that God, from His point of view, has already created everything. The end has been written just as surely as the beginning. This really strains the idea of free will, IMO, because if God has already determined that it would happen then man really doesn't choose. God chose for us when He made everything. He chose by making us the way we are. He chose by making the circumstances of our lives what they are. He chose by giving us the parents we have, country we live in, tragedies we suffer.
In the scenario where man has actual free will, then the change in plan wouldn't mean a mistake, rather, a changed attitude towards man based on man's decision. Like in Jonah, God changed His mind about destroying Nineveh. It wasn't because the plan was faulty, it was because God is Just and Merciful and He responds when people repent.
I think you unnecessarily tie sovereignty to foreknowledge, too. God being sovereign doesn't mean He's moving everything around like some grand chess master playing a game with Himself. Rather, it just means that God is the owner of everything, and He is the ultimate authority. God can intervene here on earth if He wants, but He chooses not to do so in a way that intervenes with free will.
It seems to me you want to have it both ways. On the one hand you say the people of Nineveh repented because it was God's will that drove them to it, yet Jesus says it was His will that Jerusalem repented, yet they did not. Is there conflict between the will of the Father and the will of the Son? I think not.
I'd like to hear what you think being made in the image of God means. From my perspective, I can't see how you can reconcile an inborn propensity to sin with the image of a totally good God. If God was totally good, and we were made in His image, where did the propensity to sin come from?
Where do our standard come from? I'd say the inner witness of the Holy Spirit, working through the reading of Scripture is a good start. The problem with that is that we all take different meaning from what we see there. This dialog is a good example. So, how does absolute truth fit in? Well, I believe there is absolute truth, I challenge the idea that man is somehow entitled to it, or that it is even something we are capable of attaining. In fact, I think this is at least partially what was behind the fall. The tree of the Knowledge of Good and Evil represents the ability to tell right from wrong. Man was never supposed to try to figure everything out on his own. Man was supposed to walk in the Garden with God and let Him be our guide. This is why the New Covenant is written on our hearts. I think this is one of the promises that has been partially fulfilled and when Jesus comes back the relationship will be perfectly repaired and we will have direct access to the Truth. Until then, I think it's best to be open about things that we can't know for sure.
You say you believe God wants humanity to glorify Him willingly, but how can this be true if God made the world knowing before hand that most people would never even hear about Him? It doesn't seem like He really wanted the Chinese, Indian, African, or Muslims to glorify Him if He just made them to live their entire lives in ignorance of Him only to suffer Eternal conscious torment for it.
Free will means that when we are presented with a choice, we really have a choice. It doesn't mean we are presented with every choice available. Some people are never presented Jesus as a choice so they can't choose. Did God want them to chose Jesus?
I totally disagree that you need Hell for moral reasoning. In fact, I find it counterproductive. If we go back to Jesus' favorite analogy of God as a Father, we are the children. Would a parent want their children only to obey because they are threatened with violence? Don't parents want their children to eventually learn what is right and wise and then choose to do those things on their own? Further, you complicate the issue of justice with the idea that people who God made predestined to never hear the gospel or accept Jesus, with the express purpose of torturing them forever.
I don't think I'm mixing up God and man with my understanding of inborn inclination to sin, either. If God made man with the inclination to sin, and He knew beforehand that man would sin, then God is the one who invents sin by creating an agent for sin where none existed before.
In your Zuckerberg example, the simple answer is that I don't blame Mark because he didn't know this was going to happen. He's not God. If your scenario said that Mark somehow was able to see the future and he still did everything the same, despite knowing the outcome, then I would say he is morally responsible.