with saltwater it's not fish per gallon it depends on what your stock is and how big they get full grown , in my 90g I have 9 fish out of the 9 I have 4 small fish about a inch 4 medium fish about 3 inch 1 large fish about 6 inch these sizes are full grown
it depends on there full grown size aggression and how active they are ,
live aquara is a good place to look for fish as they tell you if they are reef safe how big they get and recommended tank size ,
Saltwater Fish: Marine Aquarium Fish for Saltwater Aquariums
it also depends on if they are top swimmers middle swimmers or bottom swimmers , it also depends on your scape , my 90g is wide open in the center with rock on either end and just a bridge in the center leaving lots of swimming area ,
just a note most of the bigger fish like to rearrange rocks and constantly knock over corals , with a trigger those fire fish will be dinner over time , also not reef safe
with the stock list you posted you are over stocked , that tang will grow out of that tank in no time they require a 6 foot tank or larger , so will the trigger as he will grow up to aprox 10/12 inch
of coarse all my fish are hiding lol