Thanks... I miss my old tank though (see avatar).
As for the way you added your snails to the tank; it sounds like you just dumped them out of the bag to fall through the water column? As you know now, that's not the best idea when you have predators... : P Especially with shrimp, you should carry them down onto the rockwork so as not to tempt the fish.
I personally wouldn't go DSB from what I've read about them... I'm planning on going 2-3". I'm only bare bottom now because it's pointless for me to add sand until I move.
I think you're probably good with the nass snails, but I don't think it would hurt to add a few more.
A sand sifter star isn't a decorator star. They look pretty much exactly like sand. No descriptive color at all. Those other stars are not really reef safe, from what I thought I knew, but in looking up the stars again, they don't seem that bad. I want to say I remember them eating on everything in the tank including corals. Here is what I was specifically talking about:
White Sand Star
Sand Sifting Sea Star
Also, they are considered the 'Canaries' of the aquarium. In other words, when something goes awry, they are the first to perish. (pulsing zenia is also considered a tank 'canary')
I like to use a two part calcium/Alk suppliment. One is to boost Alk, the other is to boost Ca. The beauty with this system is that once you get your levels set (say 4.5meq/L and 450ppm Ca), you only have to check your Alk and add equal amounts of each. I use B-ionic... You can also raise it with baking soda, but you would have to look up the info on how much to use online somewhere.
I'm not sure what the going 'standard' refugium size is as a function of tank size, but I'm sure Melev's site can help you with that. I think the general consensus is to use as big as you can fit under your stand, while still being able to maintain your system (room to work on pipes/fittings/pumps, etc.)
HTH
-M