I have a very similar stocking in my 55g.
I have a hawkfish and an anthias who are pretty docile. My two false percs pretty much keep to their paly colony.
I have a sixline wrasse who has not shown any agression to other fish and spends all of his time flashing his reflection in the glass and zipping in and out of my LR.
My royal gramma on the other hand is very agressive and has staked out a very large territory that she defends.
I have added a single firefish (Nemateleotris magnifica) 3 times and all 3 times they stopped eating and died. Probably because they were terrorized by the Royal Gramma.
Recently I added a pair of purple firefish (Nemateleotris decora) as I was told that they are a little more agressive than the magnifica and because they survive better in pairs. Since adding, they are always together and have found a spot in the tank that seems to be OK with everyone.
So basically, keep track of who your agressors are or might be. In your list, I see the firefish being the target of possibly the Royal Gramma and the Sixline. I have no experience with the Flame Angel, but if you decide to ever put coral in there, they are not necessarily reef safe.
J