Wow, what a confusing read. As a newbie to this hobby, I read this forum looking for advice and seeing what is out there. I think as a newbie, I would like to suggest one thing. If you have a LFS, that you trust, go to them. I’ve dealt with the fun uglies, lost 3 clowns (one just jumped out, so there’s that), and a host of inverts. My 14 gal tank is young, just turned 8 months old. I do not have room for a QT, so when I add a new creature or vegetation, I let them sit in the water bag it came in, in my tank. My tank is also warm, compared to most tanks ( according to my LFS), it usually sits around 80 degrees Fahrenheit. I have used KanaPlex, Chemiclean, and Focus, a binding chemical for medicine and fish food.
I’m not going to tell you what to do, because honestly reading this thread confused me more than gave me information that was actually helpful. I will say, if the tank is young, like mine, maybe starting over would be the best option. I will say, that everything I have researched says copper is very, very bad for our tanks and the reefs we grow.
Good luck! I hope everything turns out successful for you.