I'll keep thinking. It's not easy to choose. I might have to suggest three or four, but maybe change my mind, too.
My understanding of the ending of Job used to be the same as yours, essentially. I thought that God shows up and essentially says to Job, "You've got no right to talk like that." And I felt that way, because God doesn't answer Job's direct question, and instead says to him, "Where were you, when I made the heavens and the earth..." and so on. That struck me as a kind of shut-down, at first.per my view of Job differing from yours, who so? curious.
I now no longer think that.
Having read the book many more times now, I've caught the thought-flow much better. As you no doubt know, Job deals with the question of pain and suffering. In particular, it's "Why do bad things happen to good people?" And I don't know a single person who hasn't asked him or herself that question at some point. I think it's a fair one.
But apparently, so does God. Because not only does God not "smite" Job for asking it, he doesn't ever tell him he had no right to ask. Moreover, he doesn't get angry with Job at the end, but with Job's friends, who were spouting all the pat and easy answers to the question of divine fairness. In fact, God says to Job, "You'd better pray for your smug friends; because if you don't, I won't forgive them for what they've said to you, my friend, and what they've said about me." So Job prays for them, and God forgives them for Job's sake.
Doesn't sound like God's mad at Job.
So what does that answer mean, "Where were you when I made the heavens and the earth"? I think the answer is this. God is saying, "Job, you come to me and ask me a question as big as the Pacific Ocean...but in your hands is only a tiny cup. You come to ask for the mystery of evil, but you are only one human, with your tiny brain. You weren't around for past millennia, and you haven't seen the future. What's more, you understand very, very little even of what's presently going on. So at some point, you're going to have to give up the expectation that at some point I'm going to explain it all to you -- not because I'm not being forthcoming with you, but because I can give you no truthful answer you can comprehend."
"So," concludes God, "you need to trust me, instead."
That, I think is the ending of Job. Not God saying, "Shut up," but God saying, "I'm just as great and good as you have always believed I am, but my ways are beyond your ways, and beyond your comprehension. Yet, if you trust me, I will remain your God and you will remain my friend."
I would say it speaks more of the graciousness of God than of Jonah's general compassion to humanity. Jonah doesn't even like the Ninevites, and in fact, wants them all under the judgment of God. His complaint against God is,same with my missing Jonah's purpose per your view.
But it greatly displeased Jonah and he became angry. He prayed to the Lord and said, “Please Lord, was not this what I said while I was still in my own country? Therefore in order to forestall this I fled to Tarshish, for I knew that You are a gracious and compassionate God, slow to anger and abundant in lovingkindness, and one who relents concerning calamity...."
He's mad at God for being kind. And God's reply to him is,
"Should I not have compassion on Nineveh, the great city in which there are more than 120,000 persons...?"
That's how he fixes Jonah. He tells him, "I'm not just a God who shows mercy to Jews, but to Gentiles as well. And you, Jonah, have more sympathy for a houseplant than you do for a human being."
Ouch. What a burn.
Hardly a Humanist message, though, since it is God who has the compassion, and humans like Jonah who severely lack it.