Both versions using 'the' seem to be referring to some context that is missing. For example "She was unable to go on their chosen date, but was travelling to Canada the following week." 'Following' follows something and I find unidiomatic to say "I am travelling the following week" instead of "I am travelling next week." But even that can confuse people: some would understand "next Moday" to mean the second Monday.
Ether, or æther, was the mysterious substance once thought to suffuse the universe and be the medium that propagated light (and radio waves once they were discovered). Before that, it was the material that suffused the realm of the Gods. So, to say that something is in the ether means that it is something being communicated from place to place; it has no precise location, just as a radio broadcast can be heard from many different places. The idea of ether as the medium for light and radio ...
Cutlery has two definitions: 1. cutting/edged implements used for serving or eating food; 2. eating utensils in general. Without further context, an American is likely to assume the first definition (knives), while a Brit is more likely to go for the generic meaning. Silverware also means eating utensils, especially silver-colored ones, though nowadays, most silverware is not actually made of silver. An American synonym that does not imply anything about the silver content (or lack thereof ...
Part of means part of something, i.e, it is less than the whole object, but a part of means little bit of something, i.e., a specific sub unit of the object.