You have made a very good observation here, I'mbigger/you'reolder. I'll start to answering the part pertaining to the stone table: all your questions have whole theological reference books trying to answer them, so I can't pretend to be able to fully answer them here.
In LWW, what law is written on the Stone table? The Witch says, "Have you forgotten the Deep Magic?... [The Magic that] is written on that very Table of Stone which stands behind us? You know that every traitor belongs to me as my lawful prey and that for every treachery I have a right to kill."
The traitor in this instance is, of course, Edmund. So what did this law (or "Magic") written on the Stone Table do? It declared Edmund a traitor condemned to die at the hands of the Witch. Through this Lewis is making a very clear allusion to Romans 7, where the apostle Paul describes how the law shows us what sin is, and because we are all sinners, we all stand condemned by the law.
When Aslan raises from the dead and the Stone Table is broken, it is symbolic of what Paul writes in Romans 7:6, "We have been released from the law so that we serve the new way of the Spirit, and not the old way of the written code," and in Romans 8:1-2: "Therefore, there is now no condemnation for those who are in Christ Jesus, because through Christ Jesus the law of the Spirit of life set me free from the law of sin and death."
One thing we need to be careful to do when we are studying the Jewish law is to distinguish between the moral laws that God gave the Israelites as his people, and the governmental laws that he gave them as a nation. There is a very big difference, and they are literarily separated in the books of the Law (the Pentateuch, or Torah). Some of the laws you mentioned, I'mbigger/you'reolder, are sanitary or cultural laws that were necessary for the people of Israel as a nation, but were not moral laws in the technical sense (though notice that to them everything was done to please God, there was no obvious division between religious and secular).
We as Christians are God's people and have entered into his covenant, but we are not (at least according to what I have learned) merely a continuation of the ancient nation of Israel. We are therefore not required to live by their ancient national laws. (To see how this issue came up in the early church and how they dealt with it, read Acts 15.)
Which laws should we obey then? To answer this question, most Christians look to the teachings of Jesus in the gospels. Look, for example, at his answer to the rich young ruler (Matt. 19:16-21) and his answer to the Pharisees (Matt. 22:34-40).
Jesus also had a very thorough and unique interpretation of how we should obey the Law. (Matt. 5)
I hope this helps a little. I sort of ran through all of this very quickly, but it was still really long!