Ok Brit, here we go! I’m going to focus on one particular piece of your question, the Creation of Middle Earth versus the Creation of our own; specifically focusing on some of the mechanisms behind them.
In the Beginning, there was only the One. Iluvatar created the Ainur in the void, and gave to each of them gifts and talents. And he lead them in the creation of a great Theme. This Theme is the creation of Middle Earth in its entirety. It is very important that Arda is created through music. For many, and possibly Tolkien as well, music is considered the highest form of prayer.
Yet, more importantly, it is in the Music of the Ainur that the reader first sees the root of the fall. It is the same sin of our own Creation. It is the sin that leads to all others: Pride.
Throughout Tolkien’s universe, he gives unceasing witness to the dangers of pride. Pride lies at the root of all sin and evil. Think of Adam and Eve. God gave them no rules, save one: not to eat of the fruit of the Forbidden Tree. In eating that fruit, they denied the authority of God, denied His trust and guidance. In eating of the tree, they asserted that they knew better than God. And so Man fell.
But to backtrack a bit…
The great Theme was underway, when Melkor thought of ways to better it and turn it to his own desires. Again, corruption and evil is born of pride. With each theme, Melkor’s grows in arrogance and bombastic pride, yet the theme of Eru is always the stronger, gently asserting itself in a crowd of turned backs.
The scene is especially touching. No matter the discord and interruption, the great Theme goes on. God is always there, asserting His will, often unheard under the bombast, but persistantly, unfailingly there for all who would but listen.
The fall of the Elves is the same, through pride. Beginning with Feanor and the Noldor, pride takes root. He denies credit and ownership of the Silmarils to all others. Out of this pride in his own craft and material possession grows greed, hate and arrogance. Instead of working with and obeying the Valar, and by extention Iluvatar, the Noldor decide they are more capable on their own.
The same is true of the grey elves, who refused to even pass over the sea to Valinor. They refused the wisdom of the Valar, in favor of the land they loved. God calls us to be humble servants of His will. We need Him in our lives, any claim otherwise is just Pride.
The pain and sorrows of Middle Earth begin and end in pride.
Think of Saruman. He believed he could study the power of the Enemy. He believed he could enter into the affairs of Middle Earth, and order his life as he wished, forsaking his duty as an Istari. Where did that lead him?
Think of Denethor. He denied all sense. In his despair, he denied hope, and took his own life. In his pride, he believed if he alone could not defeat the Enemy, no one could.
Think of Earnur. He denied all knowledge of the Witchking, heeding the insult to his prowess. He thought himself greater than all others who had already died at the Nazgul’s hand.
Think of Gollum. He prided himself in his cleverness, in taking the Ring from Deagol, in finding Frodo and Sam and in his attempts to retake the Ring. He gives up all else for the Ring, idolizing it. Where does that lead him?
The list goes on. But the key factor is that Pride is always at the heart of evil and wrong-doing. This is true both in Middle Earth and in our own.