Good questions. Sounds like you're well on your way with the cycling and with what you want to put in the tank as well. The Coral Beauty, Clownfish, and Gobies are all good candidates for your reef tank, although you want to watch the Coral Beauty. Dwarf Angels can be a little nippy at times, so do add with caution. The Sailfin is too aggressive for your setup as an adult. It could work for awhile, but would need to be put into a more active and aggressive community of fish at some point. A better choice would be the yellow tang, or a pair or harem of 3 hippo tangs, or the convict tang. Some other fish that could work in your system would be assessors, chalk basslets, hamlets, some of the smaller anthias (though they tend to be more deep sea reef specialists), chromis damsels, fairy wrasses in the genera Cirrhilabrus and Paracheilinus, possum wrasses, some of the deep reef butterflyfish such as Burgess's, Tinker's, and Mitratus, Fu Manchu lionfish, golden moray eel (this particular moray is peaceful, only reaches 8 inches in length, and has been kept in nanoreefs before), lawnmower (or "scooter") blennies, mandarinfish, a group of about 4 to 5 cardinalfish (such as the pajama cardinal and Banggai caridnal), and tank-raised pseudochromis. As far as how many fish you can keep, the inch per gallon rule is for freshwater tanks. Even the one inch per five gallon rule told to you is pushing it a little. Truth be told, though, the more important factors as to what can go into your tank are mass, girth, and bioload. For instance, you could put probably about 50 chromis damsels or cardinalfish in your tank and still be under bioload. Yet if you had triggers or surgeonfish or large angelfish, you wouldn't be able to keep near as many, both because of aggression issues and also because of the fact that these fish are much larger than chromis, are messier and bolder feeders, and put more pressure on a tank ecosystem's bioload. The bottom line is that a lot of common sense can help you make some of these decisions, and the fact that you're on this board and trying to consult the sources that can give you good information is a great start. Best of luck to you with your tank, and hope this helps.
Brad