[Raynor]

Tolkien's tinkerings with her in letters and later notes, adding elements of the Mary myth to her persona only serve to make her seem flat and one-dimensional, and deeply un-womanly, as though she is reduced to a mere cipher or symbol than a real character.

Considering her deeds in the first age, no amount of later "tinkering" would make her one-dimensional (to me).

Tolkien was the God of Arda, he was the only one who could create it and give it life, and that is what he did. With the letters, it's as though on the 8th day he opened the door and let some other God from another part of the void in, and we know what they say about too many cooks.

Well, I am sure the professor would preffer the term sub-creator. In the On fairy-stories essay, he states that a work is believable and can produce "willful suspension of disbelief", or more accurately, secondary belief, only if it achieves inner-coherence, which is what he tried to do all the time with his work. If you are saying that what he did was the opposite, i.e. destroying an existing coherence between the form and essence of his work, I will have to politely disagree.

This is all a bit vague, though, & hardly specifically Christian. Pity, mercy, compassion are all essential to Buddhism, for instance. What is often cited as 'Christian' themes in these arguments are actually much more universal. Tolkien certainly found them in Christianity, but he could equally well have found them in other faiths. I think a Jew or a Muslim could equally well have written LotR, or a Buddhist or Hindu or Sikh. I'm also pretty sure that any readers of LotR who followed those faiths would have no issues with the philosophical underpinnings of the work or feel they were at all strange.

If what you imply is that if you want to make a christian/catholic work you must use only elements that are specific to this religion, then I disagree

The specifics of Christianity (Incarnation, Sacrifice of God for the salvation of the World, Resurrection, etc) are absent from the story.

Having those in the original form would have been as much as an allegory as you can possibly have. Of course, I could point out to the presence of the Gods who are Incarnate and whose eyes are not dimmed and whose hearts are not hardened; or to the foretold coming of Beren who descends into hell and brings out the light; to the sending of the imperishable flame at the heart of the world, making its foundations good and healing creation from inside; or to the second coming of Turin, who will slay Morgoth; or to the foretold coming of Eru himself, to heal all Creation.