AC, I can't answer all your questions, but I did arrange this for guitar 7 years ago and my notes of the time read as follows.

When Kemp Did Dance Alone
Thomas Weelkes c.1575-1623

The author of this tune (also known by the title of the words it was later attached to, 'Robin Hood, Maid Marian and Little John are gone') was Thomas Weelkes, an English madrigalist and church musician, described by a contemporary as "a drunkard and notorious swearer and blasphemer"! He lived in the same period as William Shakespeare (1564-1616) and William Kemp (c.1560-c.1603), an actor and clown in Shakespeare's company, after whom this tune was named. The title refers to Kemp's morris dance all the way from London to Norwich in nine days (twenty three if you count the rest days) in 1599. Although he did dance alone, he had with him Thomas Slye, "Taberer", William Bee, servant, and George Sprat, his overseer, "that I should take no other ease but my prescribed order".

Hope this helps.