i've partially read the first LOTR, and also put it down due to the plodding pace. based on what i remember plus fandom osmosis:
>which equates disharmony with wickedness
>and that to disagree with them, or resent them, or rebel against them is a sign of wickedness
orcs and trolls are created "damned", inherently evil and unable to change that. i've heard tolkein said he regretted that bit of lore exactly because it's against the concept of grace.
frodo and gollum are paralleled. gollum kills someone to acquire the ring; frodo volunteers to carry it because no one else will, and attempts to resist it. bilbo carried it and used it for a long time, according to the Hobbit; i've heard tolkein said the discrepancies between Hobbit and LOTR are because bilbo lied. perhaps then, bilbo was not as nice and unaffected by the ring as the Hobbit claimed.
bilbo left the shire in the middle of his joint bday party with frodo. frodo left shortly after, and frodo eventually left for the Undying Lands. maybe the real function of the ring is death. accepting it like gollum did, like bilbo took it, like the other people accepting the sibling rings linked to it, requires that you either leave your world behind or that "who you are" dies and what's left becomes corrupt. like a body without a soul, an empty shell. to return to the place you left makes you a sort of zombie, that "disharmony with god" type of thing, a wraith among the living seeking to bring down everyone else for company in their misery. perhaps bilbo was not affected like frodo because he did not know what the ring was.
if the ring's function is death, maybe it turns hobbits invisible because hobbits can move between spirit forms like wraiths are and the physical world without becoming corrupt. i've heard the undying lands used to be freely accessible, not a one way trip; if so, that would parallel the hobbits' ability to move between worlds. if the ring is death, perhaps morgoth putting all his soul into it was sort of him becoming the lord of death, like a satan figure. it feels like there's a relationship between frodo volunteering to carry it and morgoth creating the ring of his own will; they both freely chose. if morgoth and illuvitar aren't terribly different, perhaps they are different types of life and death: illuvitar and the undying lands as a spiritual form of heaven, wherein you physically no longer exist in the mundane world, vs morgoth's immortality of the body on earth and death of the soul.
maybe the world is called "middle" earth because it's between the lower world of soul death and the higher world of bodily death. the parallel between frodo and gollum has the sense of "there but for the grace of god go i"; maybe the orcs and trolls and gollum all chose to spurn grace, spurn light and eternal spiritual life to instead choose indulgence in physical life. if so, the "indulgence" is likely a play on the christian idea of "the flesh is weak", and that flesh itself is damned and unclean due to original sin. it could also be a form of the christian "three enemies of the soul"/"three categories of sin", which are the world, the flesh, and the devil.
if that's true, then perhaps orcs and trolls are inherently damned because they are created as a body without a soul, like a zombie. maybe orcs, which i've heard are twisted forms of elves, actually are elf bodies raised from the dead via some kind of necromancy. in the movie they're born from the dirt, which kind of feels like a play on the christian idea of "from dust to dust" wherein humans are created from dirt and will return to it in death.
light and dark, illuvitar and morgoth, the undying lands and the depths of greed where the balrog lives, could all be different forms of eternal life. hobbits going invisible could be them giving up their bodies willingly, taking a sort of true/eternal form like the invisible hand of god working in the world. maybe tom bombadil could not be tempted by the ring, by eternal life, because he never existed in bodily form--maybe he's a sort of solid spirit, master of nature. goldberry, his spouse, is called the river-daughter. water is cleansing and life giving, like the religious concept of baptism cleansing sin. cleansing death, i think, since they're called "life giving" and one gets to the undying lands by *sailing*. if that's true, then going to the undying lands is a "clean death" that gives the peace not found in life and allows the body to literally "rest" in peace, never to rise again.
goldberry as the daughter of the *life-giving* river--not the river itself--could be the spirit of life itself. bombadil is thought to be a type of genius loci, which IRL is the spirit of a place; he could be the spirit of the middle earth lands itself.
maybe singing, playing, food, happiness, and taking pleasure in the world (hence all the long nature walks in the books) are the elements of *satisfaction* in life. satisfaction and fulfillment could be the factors of immunity to the "temptation" of becoming a soulless body, seeking in death what was missing in life.
since the ring does not affect bombadil and he plays with it like a toy, the metatextual idea could be that he's telling the hobbits there is still pleasure and life after their task, that the ring ultimately does not affect what truly matters in the world. maybe the ring isn't standard death, but a loss of pleasure in life. that fits with gollum and frodo both forgetting bodily sensations like the taste of strawberries and soft wind.
maybe that means illuvitar isn't "god" as such; he's the representation of joy. morgoth would be its loss, and the ring would be morgoth--who already had eternal life--volunteering to make himself a permanent physical presence on middle earth. he wouldn't be sin, he's a soulless existence, the opposition to pleasure in the flesh and the world. in destroying the ring and thus morgoth, middle earth passes into the "age of men" without magic and without eternal beings like the elves. destroying the ring would be destroying dissatisfaction itself, and passing to the age of men is allowing men to exist in peace and happiness forever. sort of like an eternal eden, which sam as the gardener cultivated and kept alive for frodo. maybe bombadil isn't just the spirit of the world, but a spirit of eden, a safe world without conflict. aragorn's rule could be heaven on earth, an eternal union of body and spirit for humans like the hobbits already had.