AFAIK, there is no way to get more than the maximum of 50 notes returned with the call:
Notes returned from the API *do* come with a timestamp for each Note.
They *do not* come with the meta information about Reblogs, eg:
"SomeUser27 Reblogged this from AnotherUser43"
It's odd -- to get both pieces of information (the timestamp, as well as the "Reblogged from") you would have to combine page scraping with the API.
Also of note, is that the API's Notes don't include when a post is Featured in a #Tag, eg "This post was Featured in #Artists on Tumblr"
I'd love to be corrected about this, or learn about some secret undocumented API features, but I think this is the state of things.
Felix