The 6th commandment is actually: Thou shall not murder. The difference is that murder is an unlawful act whereas there may be a lawful reason to kill a person. There are even laws in the Mosiac Law that further this and we seem them mirrored in our modern laws.
The 7th commandment is directly related to the real reason marriage was even created: property rights. Prior to currency, wealth was measured in land and livestock. Women were prohibited from owning property. Therefore, it was important for men to produce a legitimate male heir to pass his wealth on to. Sleeping around and producing multiple male heirs with multiple women presents a huge problem.
The 10th commandment: See "The 7th commandment".
Commandments 1-4 are all BS as they, like all religions, are just a tool to control the masses.