A Google search yields several JSTOR articles--you can't click through directly from those links, but you can go the JSTOR page through Columbia's electronic resources and read either one of those articles. Here is a decent wikipedia entry on the Dutch garden (more geometrical than the "English style" during this period). There are a lot of good books about gardening and English literature--ask me if you want more details.
2. Betty’s snuff-box (265), and the topic of servants.
These images will give you a feel for the visual style of eighteenth-century snuff boxes. A useful page with lots of details concerning eighteenth-century clothing styles--scroll down (or search) and you will find a brief discussion of the snuff box as accessory. You could also try a keyword search in ECCO to dig up literary references--there are very well-known ones in Pope and Sterne, among others. Keyword and subject searches in CLIO led me to the realization that there seem to be two different books called "Snuff and Snuff-boxes". In short, the snuff box takes us to a world that is fashionable, luxurious, commodity-oriented and implicitly imperial... For more details on servants aping upper-class manners, start with J. Jean Hecht's classic The Domestic Servant Class in England
and Bruce Robbins' excellent The Servant's Hand: English Fiction From Below.
3. Anna on Betty: “Does the Coventry Act extend to women?” (276). That link's to the Encylopedia Britannica article; it should be you get asked for your Columbia uni and password and then click through straight to the entry, but just in case not, I'll paste in the relevant bit:
In December 1670, during a debate on a playhouse tax, [Sir John] Coventry hinted that King Charles II's interest in the stage was confined to actresses. He was waylaid (December 21), and his nose was slit by some guards officers led by Sir Thomas Sandys. Parliament delayed business until the passing of the Coventry Act, declaring assaults accompanied by personal mutilation a felony without benefit of clergy. An attempt was even made to bar the royal prerogative of pardon that had been exercised to protect the assailants. The king was shielded from further repercussions by an organized court party majority in the House of Commons.4. Anna to her mother: “I desire my hoop may have its full circumference. All they’re good for, that I know, is to clean dirty shoes and to keep ill-mannered fellows at a distance.” (292) Here's a good link from an exhibit at the Met with a picture of an actual hoop petticoat--take a look! The paintings of artist Joseph Highmore, including illustrations of Richardson's novels.
4. Clarissa, speaking to Lovelace after she has gone off with him: “But here, like the first pair, I at least driven out of my paradise, are we recriminating” (Letter 98, 393). An (unannotated--I think the editor of the Penguin edition must have been overwhelmed by the sheer notion of annotating such a long novel, and I do not blame him!) allusion to Milton's Paradise Lost... but was Harlowe Place really a paradise? What does it mean that Clarissa keeps on thinking of herself as a character in literature?!?