well first lets dispell some of the incorrect information you listed
The filter you listed, don't use it. Filters for saltwater tanks are very different than those used on freshwater tanks, or should be anyways. The "best" (one man's opinion) filter setup for a saltwater tank is plenty of good liverock (1.5-2 lb/gal, your quoted 15-17 lbs would be good for a 10 gallon tank), good water flow in the tank, and a quality protein skimmer. Maybe a deep sandbed. I'm not positive about nano cubes, but I believe skimmers are still suggested for the very small tanks. Perhaps you could get away with just doing frequent water changes though, hopefully one of the guys on here who are familiar with very small tanks can chime in.
On the subject of sand, 2.5" would be a bad idea. You want either 0.5" or less, or 4"-6". Not in-between... the deep sand bed (4" or greater) will allow anaerobic bacteria to grow in the depths of the sand bed where oxygen can't reach, which will provide very nice nitrate removal. Half an inch or less is just for looks, if you want sand but don't want a deep sand bed. If you go in between those depths, your sand will trap organic matter and allow it to decompose without being removed by your protein skimmer, and pollute your water (but won't be deep enough to allow denitrifying bacteria to grow).
As for the flourescent lighting, that's also something I wouldn't really recommend. If you aren't keeping corals, then maybe it will be OK, but even in FOWLR tanks at least PC lighting is recommended. You can get a small PC fixture with a 10000K and actinic bulb for pretty cheap. Or, if you buy an all-inclusive nano cube setup, it will likely come with one.
In addition to the things you listed with the corrections above, don't forget about RO/DI water (don't use tap water for a saltwater tank), test kits, supplements for at least alkalinity and calcium, salt mix to make new salt water for water changes, etc. RO/DI water can be bought at most local fish stores for pretty cheap, I used to get a 5 gallon bucket full for $2. You could get a home unit to make your own, but if you're looking to save money and don't mind lugging a bucket or two to/from your LFS, then you should probably just go that route. Also, a small powerhead or two to create some good water flow in the tank (water should not be stagnant in a saltwater tank).
be limited on the fish you can keep in a small 10 gallon tank, just a couple of small fish and some inverts like crabs and shrimp. Adding corals will definitely make the tank look cooler, but the stuff I said above (improved lighting, correct filtration, etc...) will be super important if you are keeping corals.