Do I have to download the whole wallet to verify things?
It appears so. I just ran across this pdf guide on the Onion forum,
https://deeponion.org/community/attachments/deepvault-manual-pdf.5297/ and it does state your wallet needs to be up to date. I'm still not sure how to use it though, as the screen shots show a wallet with a "DeepVault" tab... My wallet does not appear to have such a tab currently.