How did Gollum physically change after finding the Ring?

Question

To be clear, I don't mean "by what means did the Ring physically change Gollum?", but rather "what were the overall physical changes affected on Gollum by his experiences after he found the Ring?". And by physical changes, I don't mean longevity or invisibility. I mean changes to his long-term physical form and appearance.

In the book The Two Towers, Gollum is effortlessly climbing head-first down a nearly sheer cliff face which Sam and Frodo only descended with great difficulty and the help of a rope. We read that he either had sticky pads on his fingers and toes (Tolkien compares them to those of an insect; I imagined a Gecko or tree frog), or else was able to use his "soft clinging hands and toes" to find and use "crevices and holds that no hobbit could ever have... used". It is strongly implied that Gollum does NOT, in fact, have sticky pads on his digits, but is using handholds and footholds that no hobbit could have used.

[As an out of universe side-note, I know many rock climbers, including free-climbers (i.e., rock climbers who don't use ropes); their hands are invariably covered in callouses and as hard as rocks themselves, so "softness" isn't particularly useful for climbing. In fact, as someone whose hands are huge, but delicate and soft as a baby's bottom, and who has only gone rock climbing a couple of times, I can assure you that soft hands are a serious disadvantage when rock climbing - your hands end up covered with more popped blisters and raw, bloody flesh than skin. Of course, Gollum isn't a rock climber, but he live in rocky caves for hundreds of years, so he should have callouses aplenty, not soft hands and toes. But I suppose this is neither here nor there.]

This was a bit perplexing to me because as we know, Gollum, however ghoulish he has become, is still technically a hobbit, as he has always been. So a hobbit was using handholds and footholds that no hobbit could ever have used.

This suggests that Gollum is anatomically very different from an ordinary hobbit in ways beyond his pallor, hairlessness, and large eyes. So I am wondering exactly what physical changes Gollum underwent after finding the Ring. Some may have been caused by his environment rather than the Ring itself. For instance, Gollum spent centuries in the dark; I assume this is why he became pale, and his eyes became larger than normal. He didn't eat much, or particularly well, which may have caused his extreme skinniness (especially relative to other hobbits). He never saw a dentist or brushed his teeth, so most of them fell out. He is centuries old and has a terrible diet, hence his baldness, perhaps.

But how else did he change physically after finding the Ring?

Answer 1

Since no one has offered an answer, I will answer my own question. I will, however, refrain from accepting it for a while, in the hopes that someone will submit a better, more detailed answer with better citations/references.

The Tolkien Gateway entry on Gollum has a section devoted to his appearance, which reads as follows:

Sméagol was a Hobbit, but he spent long centuries (thanks to the Ring) in darkness and damp, influenced by its evil power. It is possible that thanks to his hardy Hobbitish nature that he was not reduced to a wraith. However, he was reduced to a small, extremely thin and wiry person, with scrawny neck, pale skin, flat feet, long thin hands with clammy fingers, and large pale eyes that seemed to glow. His sense of sight, as well as his hearing and smelling, were very good, due to the time he spent underground.

He could move and climb silently like a spider, and although he had only six teeth left, he could give deep bites, even able to bite off Frodo's finger.

We can compare this to the description of hobbits on Tolkien Gateway's entry on them:

Hobbits were between three to four feet tall, the average height being 3 feet 6 inches, with short legs slightly pointed ears and furry feet with leathery soles, resulting in most never wearing shoes. Early in their recorded history, Hobbits were divided in three kinds with different customs and temperament. The Stoors grew facial hair and had an affinity for water, boats and swimming and wore boots; the Fallohides were fair, tall and slim, an adventurous people, friendlier and more open to outsiders. Finally, the Harfoots were the most numerous and instituted the living in burrows. In later days the Harfoot traits became the "norm".

In a letter to his American publishers, Tolkien described hobbits for the benefit of artists hired to do illustrations for his books:

I picture a fairly human figure, not a kind of 'fairy' rabbit as some of my British reviewers seem to fancy: fattish in the stomach, shortish in the leg. A round, jovial face; ears only slightly pointed and 'elvish'; hair short and curling (brown). The feet from the ankles down, covered with brown hairy fur... Actual size...say about three feet or three feet six inches.
-J.R.R. Tolkien, Letter 27

For whatever reason, Gollum became slightly taller/longer, his hands also increased in length, his feet thinned out, he lost his hair (all over - from his head to his feet), his eyes grew larger and took on an eerie glow, his teeth fell out, his skin color changed (he is sometimes described as pale, but more often as black, so we don't know for sure what color he was), he became extremely gaunt and emaciated, his head seemed disproportionately large (probably because he was so thin, rather than because his head itself expanded), and his motions became less human-like and more akin to a spider, squirrel, frog, or snake (he is compared to each of these at different points in the story).