Yeah, your sandbed might pose problems if you go with the goby/pistol shrimp pair. They typically need at least 3 inches, and mine seem to like sugar size (or a little larger) sand (but they may do fine in coarser sand/aragonite, I've never tried using that as substrate). Although, the mandarin would be an awesome addition, and a good replacement for the goby/pistol shrimp pair I recommended. All of the other fish you mentioned seem like great additions (except the 6-line I've heard can get quite aggressive/territorial, but I can't say from experience; plus your tank should be big enough to reduce any aggression on one fish).
As for corals/clams... I would definitely try to add most (if not just about everything) that you want before the Flame angel, since they seem to be attracted to the mucous that most corals (and some clams) will excessively exude when first introduced (from stress), which will further stress the animal. If you add these items first, then there is no excessive mucous that the Angel will go after, and even if the Angel does nip at them from time to time, the animal should be healthy enough to not be overly stressed by this irritant (that is IF the Angel even nips- which again hadn't happened with me possibly because of feeding the fish well in my tanks).
What other type of fish are you looking for (i.e., more bottom-dwelling fish, active swimmers, rock-dwelling, etc.)? Fish are what got me into saltwater, and a diverse group of fish remain a necessity for any tank I set up, so I have some pretty good info on different type of fish if you ever have questions...