Re the composition of those hooks, I wouldn't want to say anything without some form of analysis first, and we haven't got anything like this lined up. Sorry.
Re a change in the sperm whale diet since Clarke's earlier work, it is certainly possible. I am convinced that a number of the larger, slower-moving cephalopods that we encounter (or used to) around New Zealand have been or are in the process of being systematically wiped out by large, relatively fast-moving fishing nets. Protecting the whales is one thing, but unless we protect its prey the whole thing is farcical. Ooops, I'm not allowed to express opinions like this.
Admittedly data is poor - all I have to go on is the fact that several large-bodied squid species have all but vanished from our waters (in areas where they once proved common), but I think that temporal changes would be apparent in sperm whale diet composition in New Zealand waters ..... if only we had archival samples (and we don't, and there has been very little work done on sperm whale diet down this neck of the woods).
I don't know what recent information the Japanese have published on the whales diet, but (intuitively) I don't think it would have changed that much in Antarctic waters - there's simply been too little fishing activity down there to alter deep-sea squid population dynamics (unless some other factor is responsible for the observed local changes).
It certainly is worth exploring.
Cheers
O