The bioload on your tank would be way too massive. Your tank would crash, the fish would die. Go with a larger tank, or get smaller fish. Also do some GOOD research. LET your tank cycle. I cant stress that enough, DO RESEARCH!!!
The panther Grouper alone will grow atleast 16" long. Its cruel to have a fish until it becomes too big and take it back. Consider this, what if your LFS wont take it back?
Your friend apparently had no idea what he was doing. Feeder Guppies and Brine Shrimp are by no means healthy. Those fish must have been miserable crammed in that 55.
You can easily file down their teeth with hard shell shrimp, other foods that they will eat are krill, frozen brine shrimp, live shrimp, open mussels, squid, just mainly anything you give them they will eat.
Be very weary of putting your Longnose Hawk in with them. Longnoses are very agressive toward smaller fish, and can easily eat most any of the fish you listed. Dont be fooled by their mouths, they CAN open very wide.
Wow, that Trigger rules out EVERYTHING you listed. if you want to keep the trigger, I would reccomend it be kept alone. PLEASE don't buy the trigger and the Lion and place them in the tank together. You will end up with a horrible mess and the horrible emphasising whats going to happen to the...