Who is God?

As I've stated in my introductory post, some of my topics will be more "touchy" than others. Well, this is one of them. I will present my thoughts, but the main purpose of this is post is for you viewers to consider and respond. If you don't feel like you have something to say that's cool.
    Being raised in a protestant environment while in the same time experiencing a secular way of life I want to observe that many young Christians do not really put thought in their beliefs. "Jesus died on the cross for my sins." Ok, but why? How does this sacrifice affect your life today? So the questions I'm bringing forth shortly is striving to do just that. Think.

         "Reason can be used to determine that God exists, but it falls far short in discovering all of God's qualities."  
                  Thomas Paine

If we could understand God's qualities then He wouldn't be God now would He? The Bible serves as the main source of information in understanding the sides of God we are allowed to. As I've been studying the Bible here and there, recently, I've come upon certain passages of contradiction between the God presented in the Old testament and the New. Here is one:

In the Jewish Torah God has given the Israelites a set of strict laws they should abide to and follow. There's a specific passage in Leviticus 20:10 on the issue of adultery.

"'If a man commits adultery with another man's wife--with the wife of his neighbor--both the adulterer and the adulteress must be put to death."

                                                          
In the Jewish traditions, executions were committed by the entire community, usually by lethal stoning. Even in Arabic nations today, that's how adultery is punished. This is a without a doubt gruesome, and ruthless punishment. God ordered it. Even if it has deep reasons behind it, if you believe that the Bible is the Word of God, then he really gave this order.

   Hundreds of years after this command was written, a Galilean carpenter, considered by many, the Messiah, came upon such an execution in Jerusalem. The religious leaders were aware of his "heretic"- for them- teachings. He basically claimed that he has come to fulfill the prophecies of Isaiah. This statement on its' own caused controversy. When they saw him, the leaders tried to trick him by asking him what they would have them do. If he commanded them to stone her, he was going against his own teachings of forgiveness and compassion. If he did not allow them to stone her, he was going against the Law of Moses. Jesus' answer was witty, clever, and unexpected:

      "You who have never sinned should throw the rocks first."

Nobody moved. Slowly, the leaders and the crowd dropped the rocks and left. My question is: Doesn't Jesus still cancel out the Law of Moses? There is nobody who hasn't sin. Why place that law in the first place? Is Jesus truly the God who placed that laws of the Torah?  An answer I usually get is that "Jesus does not cancel the Law, but fulfills it. What does that mean? Why did he have to become human to fulfill it?

I believe to have some answers to these question, but i want to hear other opinions. Tell me...