I hesitate to counter your nitpicking with more nitpicking, but I do agree that "understanding these issues fully can help you make better rhetorical use of English". And so, I'd like to correct some of what you write about the split infinitive. The story is somewhat more subtle and interesting.

The well-known story of this silly prescription was that it was decided in the 18th century that, since you can't split infinitives in Latin [Latin infinitives are a single word], you shouldn't split them in English either.

This well-known story is actually a myth that has no factual basis. It is not true that the prohibition against split infinitives was decided in the 18th century (they started debating it mid-19th century), and more importantly none of the grammarians railing against it in those times based their arguments on anything to do with Latin. Never happened. The story seems to be a modern 20th-century invention, and has spread widely among those who oppose prescriptive grammarians because it makes them look very silly. It is repeated in many popular articles and books (e.g. Pinker's The Language Instinct), but for all that is completely untrue.

The interesting question, then, is - why did prescriptive grammarians of the 19th century start railing against the split infinitive, whereas the grammarians of the 18th century didn't much care about it? And the answer is, in the 18th century the split infinitive largely wasn't there. There are some examples we can find going back all the way to the 14th century, but they are rare examples. In fact, if you just read some random 18th century prose, you're likely to quickly run into phrases that sound a little awkward to the modern ear, because they seem to intentionally avoid splitting the infinitive. But those authors didn't try to write awkwardly or intentionally avoid the split infinitive (which wasn't known as a prohibition). They were using the conventions of their time in which it was a rarity.

In the 19th century the split infinitive started occurring more often (perhaps became a fad of sorts), and that's why the grammarians noticed it. Ever since then, despite all their efforts, it has only grown more popular and accepted. And yet minding your split infinitives is not bad advice to a writer (although wholesale rejection is decidedly silly), because, when overused, they tend to sound gimmicky and tinny (to forestall the obvious objection "anything is bad when overused": true, but split infinitives get there faster. You can't easily go wrong with sentences filled with "to X Y-ly", but do just a few "to Y-ly X" in a sequence, and it begins to look weird).

(I also disagree with your praise of Pullum's persistent critique of S&W; there's much criticism that can be made of that book, but it deserves criticism made in good faith. This blog post (not by me) offers a few clear examples of what I found distasteful in Pullum's bombastic approach.)