The first born who were killed in Egypt were the first born of any coupling. This was to reveal the immorality of Egypt and why God needed to get the Jews out of Egypt. To get them away from an immoral society.

The reason for the Pascal Sacrifice before the plague of the killing of the first born was that God wanted to see that the Jews were willing to take action for their freedom.

The plague of darkness was much more than three days of darkness. According to the Torah, Egypt was a land of darkness while the Jews, if they follow the Torah are in light.

A free person has to be responsible with his time. A slave does not. That is the reason that the first commandment is declaring the new month. The Jews were being freed for a purpose.

The purpose of freeing the Jews from slavery was that they should be a Godly people. This is expressed through the commandment of declaring the new month. God is setting the people up to be a nation.

Aaron was Moses's spokesman not just to Pharaoh but to the Jews as well.  The reason was that he could empathize with the slaves in a way that Moses could not.

The purpose of the plagues was to teach that all are human, that all are equal before God.

Pharaoh presented himself as a god. His authority was based on this. When it was proven that he was not a god he lost his authority. 

Getting the Jews out of Egypt was easy job. The hard job was to make the Jews into a nation.

All the plagues in Egypt could be explained as happening through natural means. The fact that Pharaoh could not understand that it was the hand of God tells us the real problem in Egypt.