The rule is easy to articulate: Short phrases, such as quotes, are not copyrightable because they lack sufficient creativity and so, therefore, those phrases are available free for all to use.
Applying the rule, as you note, is a real bear. But that challenge is no different than applying any other rule we live by - do unto others, use reasonable efforts to satisfy a promise, don't take more than you need, etc. The legal community does not make rules difficult to follow, rules are inherently difficult to follow. The legal community's job is to put meat on the bones and try to explain how, as a practical matter, to follow the rules.
With regard to the copyrightability of short phrases, if a short phrase is the "heart" of the work from which it was excised, then it's unlawful for anyone other than the copyright owner to re-publish the phrase (in literary or art or any other form). Lots of ambiguities in there I know: how short is short? what is the heart of a work? what if the phrase was not part of a larger work? All good questions with answers that will be specific for each phrase sought to be used.
As for your categories of quotes: You can freely use all quotes from the first. You can freely use all quotes from the second so long as they are "short" and, while not legally required, you should attribute the quote to whomever came up with it. As for your third, there's the rub -- each phrase must be evaluated individually. While the phrase "ET phone home" is a very short phrase, it is protectable under copyright law while much longer phrases, sentences, and even whole paragraphs that relay facts are often not protectable.
There's no getting around the fact that you'll need an attorney to "clear the rights" to sentence-length or greater quotations that you intend to morph into jewelry. In fact, because you're using the results of another's intellectual efforts in a way different than how the result of those efforts was intended, a court would likely more aggressively protect that result (the quote).
In short, when trying to apply life's rules guidance is often needed and welcome. Which is why we have preachers, shrinks, and lawyers. Good luck.
As Attorney Ballard's answer eloquently explains, the rule that "short phrases" aren't copyrightable is nuanced, so like every rule, it has exceptions. Legal questions are rarely answerable without a review of the specific facts, and the answers are usually "it depends," so there's reallly no substitute for an actual consultation with a lawyer about your particular query.
To elaborate on the general rules, there's no list somewhere with non-copyrighted quotes and copyright ones, but one bright line rule is that anything you use from the 18th and 19th centuries, if it had a copyright, is now in the public domain because the authors are long dead. Those quotes can be freely used. PLease see the chart linked below for public domain timeframes.
Using your contemporary contacts' quotes is probably ok, depending on how short their quote was and how central it was to their entire work that you're taking it from. But as a practical matter, this category of sources is both the most likely to know about your artwork and the most likely to claim that their rights were infringed, so you might be best off forewarning them and advise them that this flattering use of their words will be accorded appropriate credit (on the work itself or your packaging) when you market this artwork and getting them to sign a release.
Taking quotes from books is probably ok, since as matter of fair use, with one of the factors being the relationship between the amount of the work taken and the work as a whole, it's unlikely that a sentence or several sentences could make up more than a tiny fraction of the whole work. Another fair use factor is whether your use intrudes on the market for the original work, and your art wouldn't tread on the market for a book.
But that's copyright law. You could still be held liable for unfair competition for making a derivative work out fo someone's copyrighted book and trading on their work's fame to sell your own unrelated prioducts.
All anyone can tell you about abstract contemporary uses is whether they "probably" or "probably don't" infringe. There's really no getting around the need to see an IP lawyer for specific guidance.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.