Yes, I would move that coral to the q-tank. Go to the LFS
and get a kit to test for chealated
copper. You used coppersafe, if I remember correctly, which is chealated copper, bound to an organic substance so it will no precipitate as quickly as copper sulfate. If it had been copper sulfate you may have been alright, it precipitates (what isn't sucked up by the substrate) in a couple of days, that is why you need to keep adding it to your tank... The copper will have little effect on inverts with a hard exoskeleton, like shrimp and crabs and lobsters, I have no idea whether it would effect a sponge or not, my guess is that it isn't nearly as toxic to sponges as to other inverts.
Shedding leather...it will close all it's polyps, usually shrinks visibly, it will stay closed and shrunken for a few days and then it will expand bigger than normal. This breaks up the waxy film that has built up on the coral, the film will then begin to shed off, good waterflow aids in the process. after a day or so, it will begin to open it's polyps back up and it is business as usual. It is fairly common for this to happen when moved to another aquarium, with different lighting, water parameters, etc...