The DDR (and related tools) are excellent for producing metadata about the database structure. They don't, however, really give you a good way of analyzing the content of the database (IMHO). Don't get me wrong; that's not a bad thing (I love BaseElements). It's just not what they're designed to do.
The only way I know of to get the kind of information you're interested in is to build calculations to fetch it. There are several calculation functions that will produce your metrics for you (WordCount, GetHeight, GetWidth), and you can, of course, perform mathematical operations on dates or use relational joins between tables based on a date range (or use ExecuteSQL) to fetch metrics that way.
Since this is being done on a web content database, I suggest you build a separate FM database and use the web site database as an external source to produce what you need.