Three fish in a 5.5g tank, especially when damsels are involved isn't gonna work. I'd say, get rid of the clown, damsels, basslet and angel, then you might have room for one more fish because your gonna need one big enough that it's not gonna fit in the volitans mouth when it's full grown. And then again, you'd be pushing the bioload issue.
A lion and eel will work in a reef tank but you won't have the benefit of cleaner inverts. And again, you wouldn't want another fish since in a reef, you really don't want a huge bioload or large waste producing fish and constantly battling nitrates. Corals aren't as tolerant as fish are.