Basic information about Nagisa Kaworu, including information about his name, and basic stats (what is known).

Name: Nagisa Kaworu ()
This is Japanese-style, surname first, given name second. Nagisa () means "seashore," and Kaworu (at least the closest kanji) means "fragrant" or "sweet-smelling." So, his name basically means "Fragrant Seashore." As for the spelling, yes, it is "Kaworu," not "Kaoru." The easiest answer as to why this is so is because Gainax said so. Whenever it is written in romaji either in the show or on merchandise, it is written as "Kaworu," and when it is written in katakana, it is written as "" (ka-wo-ru). However, "wo" (is still pronounced as "o" in Japanese. The character is actually very rarely used, and almost always pronounced as "o," although you will hear it pronounced as "wo" sometimes in songs (where many pronunciation rules seem to be bent).
However, "Kaoru" is a very popular name in Japan, whereas "Kaworu" is not. So, you will often see his name mistakenly written as "Kaoru." Interestingly enough, in an old Usenet discussion (which is unfortunately not available now, as Deja.com has decided to restrict their database to the past year), some people were discussing the name "Kaoru," and were saying that the name, originally, long ago, was "Kaworu." Some Japanese parents now, though, name their children "Kahoru," mistakenly thinking that this is the original form of "Kaoru."

Also known as: Fifth Children, the 17th Angel, Tabris (Angel of Free Will)
Fifth Children: He was the fifth child to be made an Eva pilot, after Rei, Asuka, Shinji and Touji.
The 17th Angel: He was the seventeenth, and presumably last, angel.
Tabris (Angel of Free Will): Although not used in the episode, this is his "Angel name," and is used in books and on other merchandise. The name comes from the Apocrypha and Pseudepigrapha, which were writings written between the times of the Old and New Testaments of the Bible (but not considered sacred by either Jewish or Christian churches). In these writings, an angel named Tabris is mentioned who is the patron angel of free will.

Birthdate: September 13, 2000 (The day of Second Impact)
This is supposedly the only piece of personal information about Kaworu that was not destroyed. As it does happen to be the exact date of Second Impact, and because Kaworu turns out to be an Angel, the date may only be symbolic.

Blood pattern: Blue
This is the blood pattern of all Angels, and is something that NERV can detect when an Angel approaches. However, Kaworu's blood type was only detected when he activated Eva Unit 02, so it must be something that can only be detected when an Angel uses its powers.