For an eel in that size of an aquarium, snow flake would be best, it will never outgrow it.
blackfoot lions are (from what I understand) hard to take care of, and IMO, id take the fuzy dwarf or fu manch over it.
for triggers, either a bursa, pinktail or huma huma would be able to be in a 75 gallon, most other trigger get fairly large and need at least a 125.
the puffer, if your talkin about a hawaiin spotted puffer, id recommend something a little larger, because they rarely reach 4 inches, or if you really want one, id recommened that you get the trigger at the same size as the puffer, so about 2-4 inches.
instead of a frogfish, id recommened a tang or a small angel
perhaps a bicolor or singapore angel (or something in that max size range), or a hippoblue or yellow tang (or again, anything in that size range)
just my 2 cents, try to keep it below 4 fish in that tank