Yeah, Arwen saved Frodo, not Glorfindel. While I enjoyed the movies quite a bit, I was annoyed by a number of things such as Arwen's "you want him, come and claim him". I've read the trilogy 5-6 times in the past 30 years or so and I have to roll my eyes at that one. Glorfindel sets Frodo on his horse and sends him across the ford of Bruinen thereafter invoking Elrond's invokation to have the ford wash the riders away. In the movie...Arwen does it and rides across with him.
Bombadil would be extremely difficult to adapt to the screen since he's essentially insane. An immortal with unlimited powers, as he was before and he will be after. He makes Treebeard seem like a hatchling. I can't imagine how you could do Tom without going way into some weird Monty Python type of world where you find a refuge in the middle of war where people feel that basket weaving is the most important task of the day, everything else being useless dreck.
True, he was pretty loopy. I loved his portrayal in "Bored of the Rings" as Tim Benzedrine and his wife Hashberry. Strobe candles, indeed!
When they get around to doing The Hobbit, I want to see what they do with Beorn.
Not too pleased with this myself, but it is known as 'dramatic compression'. Way too many characters in the novels to include them all in the movies. I was rather fond of Prince Imrahil of Dol Amroth.