Just like how you have a fetish for butterflies, I on the other hand have a fetish for Tangs haha. If you like those large angels, y don't you start them from juvenile stage. About the same size as your butterfly.
The firefish were probably half dead from the place you got them from. I recently got 5 of them all packed in the same small bag and left them in there for at least 2 hours. no issue. no fighting. But who knows, the bag might have not been sealed properly? or not enough water in it, to the point where when u moved the bag, the firefish was just sticked to the plastic bag instead of being in the water.
It's blows the corner of your sand coz u have no opposing flow. That's y u place another wavemaker on the opposite side. For some creating good water flow in your aquarium is an art.
I think all tank got ich la, even mine. just how severe only. well, if you can tahan, 2 months without fish. I respect. salute. But if you do wanna see some life in there, just let me know k. My offer still stands for you.