Many of your questions could be answered by a lovely and talented librarian armed with a few subscription databases — Lexis-Nexis, for instance, works quite well as an “online phrase-etymology guide” to TV news transcripts from the past 20 years or so. Letterman may have been spoofing Larry King, who seemingly cannot introduce a female guest without calling her “the lovely and talented” — and, occasionally, he interjects “gee, that sure sounds like old-time radio,” suggesting the phrase has a much longer heritage. You might also be interested in The Oxford Dictionary of Catchphrases, ed. Anna Farkas (2002). The very last entry is attributed to Lisa Simpson: “If anyone wants me, I’ll be in my room.”