Hi Sarah,
Thanks for moar questions, we love them.
To answer your questions:
1. Why do some rows have more than one date? Does it indicate a date range for the item? Is there a preference for which date to use in such cases?
Unfortunately, our date fields aren't very easy to work with, in additional to the limitation of contributed metadata from our content partners. Sorry, we could not give you a clear correct answer on this one.
2. Is there a way of filtering for items that have a thumbnail_url / large_thumbnail_url?
Please try
&and[has_large_thumbnail_url]=Y&fields=title,large_thumbnail_url,thumbnail_url
large_thumbnail_url and thumbnail_url always together, if there's a thumbnail_url available, we can only filter on [has_large_thumbnail_url] via our API.
Hope this is helpful for you.
Moar questions are always welcome.
Kind regards,
Ting