First, dragons are not all powerful, and the dragons still alive in Middle-earth at the time of LotR are weak compared with the ancient dragons. In "The Shadow of the Past", Gandalf says
It has been said that dragon-fire could melt and consume the Rings of Power, but there is not now any dragon left on earth in which the old fire is hot enough; ...
Gandalf says more than once that if he regains the One, then all that is protected by the Three will be laid bare. Before Isildur cut the Ring from Sauron, the elves and men were stronger and could resist him. If I recall correctly, he had gathered the others to him before the last alliance. And since he hasn’t touched the Three directly, they could hold out ...
Frodo's parents drowned in a mysterious moonlight boating accident, possibly involving a bottle of wine or ale.
After all his father was a Baggins. A decent respectable hobbit was Mr. Drogo Baggins; there was never much to tell of him, till he was drownded.'
'Drownded?' said several voices. They had heard this and other darker rumours before, of course; but ...
No, it is not normal.
Tolkien describes Hobbit society in the section 1 of the Prologue. He explicitly singles out Frodo and Bilbo as being unusual in this:
The houses and the holes of Shire-hobbits were often large, and inhabited by large families. (Bilbo and Frodo Baggins were as bachelors very exceptional, as they were also in many other ways, such as ...
If any of the other rings were in active use, then the verse is correct.
Sauron could not discover them, for they were given into the hands of the Wise, who concealed them and never again used them openly while Sauron kept the Ruling Ring [...] yet they also were subject to the One.
-- Of the Rings of Power and the Third Age
It is not until after the Last ...
Tolkien never wrote on this as far as I know, so one can only speculate. The vast majority of dragons were killed in the War of Wrath at the end of the First Age. Indeed we do not know of any dragon alive in the Third Age other than Smaug, who was killed by a single arrow shot by Bard, a normal human, albeit a hero and a descendant of a King.
But leaving ...
It was painted green
It had a perfectly round door like a porthole, "painted green", with a shiny yellow brass knob in the exact middle.
The Hobbit - Chapter 1: An Unexpected Party
As stated in the opening of The Hobbit the door was painted green.
Bilbo paints the door from time to time, in fact it was painted just a week before the Dwarves' ...
I think you've made a category error.
The Istari are Maiar, as discussed in Part Four, chapter I, "The Istari" in Unfinished Tales. They are five individual members of that group who were given a specific task and sent to Middle-earth.
And yes, the singular is "Istar".
As your question arose while watching the movie, it may be worth noting the movie itself provides an answer to it, though only in the extended edition.
In a small addition to the Long-expected Party scene, Bilbo and Frodo share a brief moment away from the bustle of the party to hide from the Sackville-Bagginses:
After the destruction of the ruling ring, the Elven-rings lost their potency as well, becoming little more than trinkets. As it is told in the "Tale of Aragorn and Arwen" (from appendix A of Return of the King):
When the Great Ring was unmade and the Three were shorn of their power, then Elrond grew weary at last and forsook Middle-earth, never to ...
As user 8719 and Ofek Aman already said, there is no detailed description of the Nenya in the books.
But if you are thinking about the movies, the first one does look a bit like the one Cate Blanchett wore (bottom right one in the screenshot below).
Why do you think silver is innapropriate? According to Wikipedia:
Gold (Available in Yellow Gold, White Gold ...
The languages came first.
J.R.R Tolkien was s philologist, and he loved languages. So he started creating a few himself. After a while, I suppose he realised these languages could be used, and he created a world (Middle Earth) and, for it, characters to speak the languages.