An important part of understanding the laws of Moses is that they were intended as part of a government and a religion, not just a religion. Rules that seem harsh when taken out of that context and applied to personal life, such as "an eye for an eye," make much more sense as a system of governmental justice. Even in the Torah, the highest laws were to love God with all your heart, soul, and mind, and to love your neighbor as yourself.
Also, their government was patriarchal and used a system of judges decided by tribe (clan) and, in later years, chosen by kings. Their entire way of life, as a predominately agrarian society frequently attacked by raiding neighboring kingdoms, was based on following the laws of your tribal leaders, grandfather, and father.
This wasn't a matter of shooting your teenager for smarting off about a cell phone bill. It was more like prolonged rebellion with potentially lethal effects for the rest of society. A terrible monster parent couldn't just wrongly kill a disappointing child. Not only did there have to be witnesses, but the method of execution implied community agreement with the severity of the rebellion. You can't stone a person to death all by yourself.
So a law that seems horrifying to someone in our society, killing a child for disrespect, was a law to protect their society from chaos, complete with a pretty serious set of checks and balances to prevent abuse.
Another thing that's important to realize is that their laws were established in a time when bathing wasn't that big a deal, and people had very little understanding of germs or the spread of disease. Many of their laws about things like ritual cleansing and separation from the "unclean" were very effective plague-fighting tactics. The kind of thing you'd expect, incidentally, if you were positing a God. But I digress.
I barely know anything about ancient Judaic law, though, even having grown up in a Bible banging church. I would contact a local Rabbi and respectfully request his help. Most religious leaders are happy to talk about what sets their faith apart, especially if that means helping a writer get things right and not spread common misconceptions.
Good luck! It sounds like it will be an entertaining read.