I've never tried using the natural sea water products but would suggest you look into some of the reef forums for experience from other users. I do know that the major public aquariums us RO/DI water and a salt mix (with the very few exceptions where they pipe in and filter their own ocean water).
The general comments on live sand tend toward the useless (again, more harm to the wallet than any harm to the tank but providing little, if any benefit). Here again researching comments on a reef forum AND noting the experience of the discussing reefer will be your better reference.
Only your top level of sand will provide a bacteria nurturing substrate as the primary bacteria that will convert ammonia to nitrite to nitrate is arobic (oxygen loving). You also want other porous substrate (rocks or other porous structures) to grow this bacteria. Anything below the surface sand is anaerobic and can be dangerous to the animals if allowed to grow and then is disturbed. The anaerobic bacteria is an aid to reducing the nitrates (the final product of the nitrogen cycle) and you will see threads on deep sand beds (DSB) set up for this purpose. A DSB cannot be disturbed, however, without releasing potentially poisonous chemicals into the water and should not be placed in an octopus tank since the animal will, by its nature, disrupt the substrate (you can use them in undisturbed sumps but nitrate is normally controlled by water changes for an octopus environment since the octo is far more nitrate tolerant than corals).
Here is a nice article that discusses how a tank matures and why simply adding bacteria all at once does not cycle a tank. This particular article is about freshwater aquariums but the cycle discussion applies to both environments.
This article addresses the saltwater environment and talks about some of the differences between nature, saltwater aquariums and freshwater aquariums.
There are two well worn expressions use in saltwater circles, "New Tank Syndrome" and "Nothing good happens quickly with a saltwater aquarium". You can Google both to see the large number of hits on the thoughts.