Why can't fish just get along eh?
I've had two emeralds and one was out all the time munching away, and the other one hid quite a bit but did come out occasionally particularly at tank feed time.
As far as rock colouration is concerned, you would count it in months before it gets anything like the live rock you have. Maybe you could aquascape it so it provides bulk but is hidden under the live rock (once you have enough).
Scaping to the back wall is pretty much a personal preference. I've gone to the back wall but have a large cavity at the bottom. This is good as it from the front it looks solid and more bulky and at the same time allows good water penetration but bad because it's given my watchman somewhere to hide and we NEVER see him. I can shine a torch at the back and there he is and he cowers in the crevices but he doesn't come out to the front. I'm convinced we have a pistol in there which is why we don't see the watchman. I still hear loud clicks
that I can't account for.
If you have a problem getting the rock stable then just use Milliput. You don't have to stick every rock, just use it selectively on the unstable rocks.
If you stick with the island, although cleaning etc is easier, it would work out less effective for soft corals if you decided to go that route as it limits the space you have to put them.
