I haven’t got the films on DVD so I can’t check but I thought the depiction of Isildur cutting the ring finger from Sauron’s hand was actually quite well done, although I seem to remember the rest of the battle being less so.
As for Sauron’s appearance, he had, until the fall of Numenor, been able to appear wise and beautiful, although I think he lost this ability in the flood, as it were. But he certainly retained a physical body, until he lost the ring.
The relevant passage would be from the council of Elrond, when Elrond himself describes what he saw.
I beheld the last combat on the slopes of Orodruin, where Gil-galad died, and Elendil fell, and Narsil broke beneath him; but Sauron himself was overthrown, and Isildur cut the Ring from his hand with the hilt-shard of his father's sword, and took it for his own.
As for the eye, I always considered it to be a physical eye, since I first read the book at the age of 11 or so. I agree with many of you that the concept became more and more difficult to accept as I got older, and I found the Jackson depiction of it as a type of electric field or plasma to be very pleasing.
Again a relevant passage, from The Mirror of Galadriel:
But suddenly the Mirror went altogether dark, as dark as if a hole had opened in the world of sight, and Frodo looked into emptiness. In the black abyss there appeared a single Eye that slowly grew. until it filled nearly all the Mirror. So terrible was it that Frodo stood rooted, unable to cry out or to withdraw his gaze. The Eye was rimmed with fire, but was itself glazed, yellow as a cat's, watchful and intent, and the black slit of its pupil opened on a pit, a window into nothing.
And for the beam of light thing, you have to remember this was a film and all descriptions must be turned into pictures.
From the Breaking of the Fellowship:
And suddenly he felt the Eye. There was an eye in the Dark Tower that did not sleep. He knew that it had become aware of his gaze. A fierce eager will was there. It leaped towards him; almost like a finger he felt it, searching for him. Very soon it would nail him down, know just exactly where he was. Amon Lhaw it touched. It glanced upon Tol Brandir he threw himself from the seat, crouching, covering his head with his grey hood.
Some have said that Saraman was the real enemy, which I’m not really prepared to accept. He was AN enemy certainly, but was at least partly under the thrall of Sauron, via the Palantir, but I don’t think he could be considered the major threat.
Some have suggested that Saraman represents modernization and the loss of tradition, as shown by all the underground industry at Orthanc and by Sandyman’s Mill which was presumably just a watermill until Sharkey "improved" it.
Tolkien was certainly one who was upset by the erosion of traditional country life.