The distinction comes in understanding "abolish" vs. "temporary". Jesus said in Mt. 5.17 that he wasn't coming to abolish the law, but to fulfill it. The law was sent to show people their sin (Rom. 3.20; 5.20; 7.7; Gal. 5.19), and it did that. But after it accomplished its job, it was considered fulfilled (Gal. 3.24-25; Mt. 5.17). But that doesn't mean it goes away. It never goes away (Rom. 3.31). It's a law forever and for all generations. The Mosaic Law has not been superseded, but the "law" of Christ has been superimposed on it (Mt. 5.18). We've been released from the law to serve the Spirit (Rom. 7.6; Gal. 3.25-4.7).

That seems like a lot of "Bible-speak," but what I'm saying is this: The law is still there, and it still does its job of showing us that earning our way to God is impossible. Jesus fulfilled the law, and so we don't follow the Law anymore, but the example of Christ and his Spirit inside us.

"deliberately temporary?" Despite the fact that it says in numerous places that it's a law forever and all generations?

Most of the commands of the OT pertain to trying to teach people how to live. The Law was a deliberately temporary measure to tell people that they should have certain attitudes, and approach life with certain principles. He did that by commanding actions with the idea that they would see the attitudes behind them. People failed at that.

Most of the commands, while about surface behavior, are not really about surface behavior, but about holiness. There are principles couched in what seems "despicable and nonsensical" about God's character, his holiness, and how people could live lives of holiness also. So it's not so much about shellfish and animals with hooves as it is about what all that stuff represents in symbolic ways.

You ask, "Why does God seem so primitive?" One thing you must see is that God spoke into their culture in forms and language that they would understand. It's not "primitive" as much as it is culturally different than our culture. Remember that explosive cultural changes have happened in the past 150 years. You may define their cultures as primitive, but they were sophisticated in many ways, and just different than ours.

Of course God knew objective morality from the start. Objective morality is rooted in his nature. But you'll notice and in the Bible God does not dictate the shape of society. He doesn't seek to form a "perfect" society, because no society is perfect (since it is a society of fallen humans). He rather speaks into the shape of society as it exists in those times and encourages his people to live holy lives in that society. He does not dictate an ideal kind of government (monarchy vs democracy); he doesn't dictate a system of marriage (arranged vs love) or even polygamy vs monogamy; he doesn't dictate the way that a society is stratified (slaves and free); he doesn't dictate a certain sort of economy (market economy vs barter). Every social structure is flawed. Instead, as I said, his goal is to raise up a people holy to himself.

You ask why God is so bloodthirsty. It depends what you mean by that. If you mean the sacrificial system, we can talk about that. If you mean warfare, we can talk about that, but I don't just want to talk until I know what you're referring to.

You accuse God of being egotistical. Do you perceive your parents as being egotistical by requiring that you learn to obey them? I hope not. Obedience to authority is an important part of a working social environment. Are teachers egotistical when they insist that you be quiet in the classroom and listen to them? I say no. Classroom order is essential to the model of education we have chosen. Assuming that God is truly deity and divine, and that he made humans to have fellowship with him and to give them life, it makes sense that other allegiances and false divinities will deprive humans of a legitimate relationship with the authentic deity, and deprive them of life that only he can give. To insist on the truth isn't an expression of egotism, but of genuine compassion.

There are many verses in OT written in such a way as if God himself is commanding to do some despicable and nonsensical (well from the perspective of a human being in 21st century) things. Does that mean that those verses were written by human beings who just used God as an excuse? Or do you believe God actually commanded those things?

My problem with people saying that "OT" is irrelevant is that it completely ignores any rational thought as far as "why does this God appear to be so primitive?" From my perspective God cannot change his mind. He must have known the objective morality from the start. Yet somehow in the OT he appears to be a bloodthirsty vengeful and egotistical.