I found myself with some free time yesterday & updated the Wiki. It should be a little more complete, and hopefully a little easier to read. A lot of the fields don't have a description, but they should be relatively self-explanatory. I also included a SQL file at the bottom to create a table with all of the columns.
On a side note, there's actually an even more recent version of the spells_us.txt file
here (also through the official patcher) that has a few more fields, which look to still be unknown.