One problem with this is it is not clear who or what Satan is and what Satan’s relationship to God is.
No, that's quite clear
It is not at all clear, and your assumption that it is indicates that you have not understood the questions the story raises.
Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.
I suppose this book was written before the revolution. Jesus hasn't been intended yet; Satan is still head boy; he's not identified with the Serpent.
Yes, the book was written before Jesus’ time. Just how old it is has not been determined. Who are the sons of God? The term is used in different ways in the Hebrew Bible. One way in which it is used is to indicate human beings who are in God’s favor. Another is for those human beings who are leaders, those who hold power or authority.
It may be that Satan is a mytho-poetic personification of evil. This should not be confused with the reification of evil, personified as a being called Satan or the devil. Such reification is foreign to the Hebrew Bible.
Does Satan coming with them mean that he too was a son or just that he came along with them? There is no indication that he is the “head boy”. Right, he is not identified with the serpent, although the serpent too is an adversary.
Nobody's - yet. He's just skeptical, maybe a bit contrary - playing devil's advocate.
The text tells us:
The Lord said to Satan, “From where have you come?” Satan answered the Lord and said, “From going to and fro on the earth, and from walking up and down on it.” (1:7, 2:2)
Evil was not absent from the world. Given what transpires it does not seems likely that all he has done is play devil’s advocate.
That's the way the events were reported to Job; he can't know that it's really Satan manipulating them.
And neither can you. This is a mythological tale. How the author understood natural events is not clear. See chapters 38 through 40, about what we would call the natural world and its inhabitants. There is no indication that God is behind these things, they act in according with nothing other than what they are, that is, in accord with their kind. (See Genesis 1 about things acting according to their kind.)
It's only because you protect him and give him everything.
This is a question that Satan asks or asserts as an accusation. In Psalms there is a prayer for protection against evil, but the author(s) of Job does not provide an answer one way or the other. The adversary who walks back and forth across the face of the earth may or may not have eventually encountered Job at some point. All we know is that God does not stand in his way. One might give a shallow reason why he doesn’t, but it may be that the author is pointing to a possibility that is more troubling to certain believers - God does not protect you from evil. Why he suffers is not adequately answered. By extension why any of us suffer and others do not suffer is not something we have an answer to.
Because they had been told that their god was just.
As Job learns at the end, neither he nor them have an adequate understanding of God’s justice. At the end of the story Job makes the distinction between what he has heard (which proves to be untrustworthy) and what he has seen for himself. This too may be troubling for believers in a revealed religion, a religion based on what the prophets have said.
They had no authority for imagining such arbitrariness.
But this is exactly what we humans do. We attempt to make sense of things and invent answers. We often believe that we are somehow to blame for our misfortune.
I suspect this version of Jehovah is a holdover from the Sumerian pantheon.
Authors, including authors of philosophical texts , often frame their stories in terms of those stories they want to supplant. This is a well known rhetorical device. Rather than accepting prevailing beliefs they use familiar ideas and terminology to introduce change. To decide whether this is a holdover requires a detailed side by side comparison.