Why would a man be given a new name?

The Old Testament genealogies continue to stretch onward. The next well known name in the list is that of Abram, or Abraham. In order to begin research into his background, I'll again start with the primary source, the Biblical account. This starts in Genesis 11:26, but I will skip a few verses to Genesis 12:1-9:

Now the LORD said to Abram,
            “Go forth from your country,
            And from your relatives
            And from your father’s house,
            To the land which I will show you;
And I will make you a great nation,
            And I will bless you,
            And make your name great;
            And so you shall be a blessing;
And I will bless those who bless you,
            And the one who curses you I will curse.
            And in you all the families of the earth will be blessed.”
So Abram went forth as the LORD had spoken to him; and Lot went with him. Now Abram was seventy-five years old when he departed from Haran. Abram took Sarai his wife and Lot his nephew, and all their possessions which they had accumulated, and the persons which they had acquired in Haran, and they set out for the land of Canaan; thus they came to the land of Canaan. Abram passed through the land as far as the site of Shechem, to the oak of Moreh. Now the Canaanite was then in the land. The LORD appeared to Abram and said, “To your descendants I will give this land.” So he built an altar there to the LORD who had appeared to him. Then he proceeded from there to the mountain on the east of Bethel, and pitched his tent, with Bethel on the west and Ai on the east; and there he built an altar to the LORD and called upon the name of the LORD. Abram journeyed on, continuing toward the Negev.

Transition to Genesis 17:1-5:

Now when Abram was ninety-nine years old, the LORD appeared to Abram and said to him,

          "I am God Almighty;
          Walk before Me, and be blameless.

I will establish My covenant between Me and you,
            And I will multiply you exceedingly."
Abram fell on his face, and God talked with him, saying,
"As for Me, behold, My covenant is with you,
            And you will be the father of a multitude of nations.
No longer shall your name be called Abram,
            But your name shall be Abraham;
            For I have made you the father of a multitude of nations."

But the name of Abraham is not confined to Genesis alone. Other books in the Old Testament name him (the following instances are not exhaustive, and this does not include the New Testament yet). There is no mistake about the name being belonging to one with a different story:

• Exodus 2:23-24, "Now it came about in the course of those many days that the king of Egypt died. And the sons of Israel sighed because of the bondage, and they cried out; and their cry for help because of their bondage rose up to God. So God heard their groaning; and God remembered His covenant with Abraham, Isaac, and Jacob."
• Abraham - portrayed as a historical man.
• Why would God remember a covenant with a man who never lived?
• Why would God relate a detailed covenant of blessing and land (Genesis 12:1-9) to a man who never lived?
• Abraham, Isaac, and Jacob--this list of names is replicated numerous times in the Old Testament, indicating that the names must have been rather important to the Israelite people, and to God in speaking with the nation.
• Why would God hearing the groanings of Israel under bondage have anything to do with men (Abraham, Isaac, and Jacob) who never lived?

• Exodus 3:3-6, "So Moses said, 'I must turn aside now and see this marvelous sight, why the bush is not burned up.' When the LORD saw that he turned aside to look, God called to him from the midst of the bush and said, 'Moses, Moses!' And he said, 'Here I am.' Then He said, 'Do not come near here; remove your sandals from your feet, for the place on which you are standing is holy ground.' He said also, 'I am the God of your father, the God of Abraham, the God of Isaac, and the God of Jacob.' Then Moses hid his face, for he was afraid to look at God."
• Abraham - portrayed as a historical man.
• God identifies Himself as both the God of Moses' own father, and the God of Abraham.
• How could the father of someone be paralleled with a man who never lived?
• Why would Moses fear if God was identifying himself as the God of imaginary people? Who would fear the lord of an imaginary world?
• Abraham, Isaac, and Jacob--again the same genealogical list. 

• Exodus 6:1-5, "Then the LORD said to Moses, 'Now you shall see what I will do to Pharaoh; for under compulsion he will let them go, and under compulsion he will drive them out of his land.' God spoke further to Moses and said to him, 'I am the LORD; and I appeared to Abraham, Isaac, and Jacob, as God Almighty, but by My name, LORD, I did not make Myself known to them. I also established My covenant with them, to give them the land of Canaan, the land in which they sojourned. Furthermore I have heard the groaning of the sons of Israel, because the Egyptians are holding them in bondage, and I have remembered My covenant.'"
• Abraham - portrayed as a historical man.
• Why would God say He had appeared to imaginary individuals as Almighty God through their imaginary lives?
• Abraham, Isaac, and Jacob--again the same genealogical list.
• Why would God Himself reference the sojournings of Abraham, Isaac, and Jacob when these stories were imaginary?
• Why would God Himself say that He made a covenant with imaginary people?

• Deuteronomy 1:6-8, "'The LORD our God spoke to us at Horeb, saying, "You have stayed long enough at this mountain. Turn and set your journey, and go to the hill country of the Amorites, and to all their neighbors in the Arabah, in the hill country and in the lowland and in the Negev and by the seacoast, the land of the Canaanites, and Lebanon, as far as the great river, the river Euphrates. See, I have placed the land before you; go in and possess the land which the LORD swore to give to your fathers, to Abraham, to Isaac, and to Jacob, to them and their descendants after them."'"
• Abraham - portrayed as a historical man.
• Why would God map out a land promised in an imaginary covenant/with imaginary people?
• Abraham, Isaac, and Jacob--again the same genealogical list. 
• Why would the nation of Israel be identified as the descendants of imaginary men?
• How could the sons of Israel possibly be motivated to go and conquer a land promised to them merely through men whom they knew to be fictitious?
• How could the nation of Israel really look upon a land promised to imaginary individuals?

• Deuteronomy 9:25-29, "'So I fell down before the LORD the forty days and nights, which I did because the LORD had said He would destroy you. I prayed to the LORD and said, "O Lord GOD, do not destroy Your people, even Your inheritance, whom You have redeemed through Your greatness, whom You have brought out of Egypt with a mighty hand. Remember Your servants, Abraham, Isaac, and Jacob; do not look at the stubbornness of this people or at their wickedness or their sin. Otherwise the land from which You brought us may say, 'Because the LORD was not able to bring them into the land which He had promised them and because He hated them He has brought them out to slay them in the wilderness.' Yet they are Your people, even Your inheritance, whom You have brought out by Your great power and Your outstretched arm."'"
• Abraham - portrayed as a historical man.
• Why would Moses, the current leader of Israel, plead with God turn aside His wrath by remembering imaginary individuals? How could this possibly be a persuasive argument on Moses' part?
• Abraham, Isaac, and Jacob--again the same genealogical list. 
• Why would Israel be considered God's people, if so rebellious, unless the stories about Abraham, Isaac, and Jacob were real?
• Why would the land of Canaan/the Canaanites be likely to mock that God was unable to fulfill promises He never made, or made merely to imaginary people?