Hi Ben
So sorry to here about your nightmere with the fish, with my cash flow at the moment i am not sure i could bounce back from something like that, i really hope you can mate. We all spend so much time and cash to do the best for are fish and then out of the blue something like this happens, the salty side can be so cruel, anyway keep your chin up mate and keep going, you will have a fully stocked tank again soon.
I am not sure if you should hold on to the coral or not, but to be honest mate, i would not be in a any hurry to put anything from a tank that has had an almost total wipeout in my tank, but i suppose it depends on what your mate has in his, if he wants to take the risk or not, but like i say i am not sure if you could actually transfer whatever killed your fish to another tank through your coral.
My yellow tail and my leopard wrasse get along very well, they follow each other around the tank feeding all the time, although they are VERY messy when they do feed, imagine putting your hand in the tank and stiring the sand every 10 mins thoughout the day and you will get some idea.
All the best
VM