I'm assuming this is Katrina with the tank at Beach Elementary.. This is Jamie. Do you want to give Alex a call later and we can help talk you through this?
1. Emerald crabs are really cool, but yes sometimes they can be jerks. He may or may not be eating the coral though. Sometimes they are eating the algae and it looks like they are eating the coral.
2. The coral is really close to the palys and that could be causing some problems, that chalice can be pretty aggressive. But I agree with the other comment that it looks like there's some sand on it and it could be causing die off, so it could just need a little air from the turkey baster to keep it healthy.
3. The palys are fine if you aren't moving them around or touching them much (totally agree with the other comments about not trying to scrape them off). But I"m sure you can trade them in at Seahorse for something else if it is more comfortable. They look like they aren't on the main rock so I'd just use some tongs to take them out or just wear gloves to grab them