I have had several peacocks in the past. He should leave the starfish alone. He may bury it tho.
Best things to feed..
Peices of shrimp ( I buy the frozen tiger prawns and thaw out a little). I would use a feed stick or chopsticks
You also can throw some snails (narsissus, astrea) in as well.
For fun, you can throw some small bluelegged or reef hermits in as well.
They will also take other types of meaty fish related foods.
BE VERY CAREFUL of water quaility. Both of my Peacocks died due to shell disease. It is important to clean out uneaten food, and do periodical water changes.
SH