If you want corals, then you don't want a chocolate chip starfish as they are pretty likely to eat them. Sepent or brittle stars are the best "starter" sea stars, but they hide a lot.
As far as crabs, "reef safe" hermots like blue legs, red legs, and scarlets are easy. Make sure you have extra shells so they have room to grow and don't fight with each other. Emerald or red mithrax crabs are decent, but may hide a lot.
You might look at shrimp like the skunk cleaner, scarlet cleaner, or peppermints. I'd avoid coral banded shrimp unless he'll be the only shrimp in the tank.
I'd also avoid damselfish. They are very mean for their size and you don't have a lot of room in that size tank. A royal gramma or cardinal fish could work. There are also a lot of gobies and blennies that would work. Check out liveaquaria.com and filter their marine fish selection by tank size or just jump to the nano fish category.