I've re-read your thread to try to answer you better. First off, your tank and skills in putting it all together is amazing looking, :thumbsup: good job!
Second, regarding the feeding, I'd want to know, or better yet see, exactly how much food you were putting in your tank. IMO, I believe dry food had more phosphate in it than frozen, IMO I also believe rinsing your frozen food helps cut down on nutrients as well. I feed 1 cube of brine and 1 cube of mysis a day to my tank. I believe the wc I do help in not having any issues with that seeing as I'm not running any filtration other than just doing wc. Now in answering that, I'll say what I meant by under feeding an emerald crab, I mean make sure there's enough algae for them to eat. They're mainly herbivores, but will resort to eating coral or anything else if left with no choice. So, once your algae issues start to go away, feed some nori to it by rubber banding it to a rock, though not a lot so it doesn't rot in the tank causing more nutrient issues.
Finally, third, it's a very new tank and you're new to the hobby! You're going to experience the ups and downs that come with trying to mimic a stable ocean within a small glass box. Just go slow and don't rush anything, and ESPECIALLY don't go chasing numbers. Try to solve any issues one thing at a time. As far as blacking out your tank, that's not really helping anything other than releasing the phosphates back into the water when the algae dies off. Just keep the corals clean of algae and don't run the lights super long. In a couple months you'll start to see some stability in your tank and you'll be keeping and fragging sps in no time!
So keep your head up and roll through the blows that your tanks deals you, sometimes it's hard to do. I think every one of us has been to a point where they just wanted to tear it down and say (insert four letter words) and kick it to the curb. It just comes with the territory of owning a saltwater tank.