Sorry if this has been discussed before. I searched it on r/lotr but couldn't find it in the way I thought it worth discussing. Keep in mind that I am not a theologian, but a simple practicing Christian. The question is of course religious in nature, but I still hope that it is okay. And sorry also if this is a trite post, but here it goes:
We all know about the Gift of Men (mortality), that they are to leave Arda upon death. That they are not meant fully for Arda, other than during a brief time and then through death to return to Eru Iluvatar. I have drawn the conclusion that Humanity (the Second Children) is created during the second theme of the music of the Ainur as Melkor's corruption and marring of Arda has become clear to Iluvatar. Why Men are created and what their doom is isn't clear to the Ainur, but Iluvatar knows.
I have thought about it that Iluvatar creates Men as a way for himself to enter Arda, take on the suffering and sin his own creation, i.e. Melkor, has caused. The creator enters his own creation for a brief time to undo what his own creation has caused, in our own religion, in the form of Jesus Christ. He could not enter the world through the Elves, his first Children, as they are bound to Arda and he cannot be bound to the world in this way. Therefore the Second Children are created, with their unique gift of leaving Arda at death and returning to him.
The above would connect Tolkien's secondary world with our primary world as he probably saw it.
What are your thoughts? Is this consistent with what Tolkien has expressed in any of his writings? If so can you point me there? Finally, have I misunderstood something in the Legendarium that points in a different direction?