Yes, air stones are a no-no in a salt water setup. You'll quickly ruin the surrounding area with something commonly called "salt creep". tiny bubbles will pop at the surface and sling salt water everywhere. It will look like this in no time at all-
Definitely invest in a power head or two. Ecotech Vortech are the best on the market, but also pricey. A single MP40 should be plenty for your tank.
Quality liquid test kits have been the tools of choice for monitoring tank parameters, but please keep us posted on the Seneye.
in many cases fish stores don't change out their filters as often as needed, so I would suggest investing in a TDS
meter to monitor the quality of water your LFS
is selling you. If it comes in as not pure, then you'll have answered your question about whether or not to purchase a RODI
You'll need to add fish to your tank almost immediately after the cycle or your bacteria colony will not survive. 6 months without fish is too long IMO
. Inverts are more sensitive and should be added after.
As for the sump, what components will you have in it? This will dictate how many partitions you'll need and also, the inside dimensions of the stand would be helpful. Bottom line is you should build your own if possible.