Becka Savage chops down the 'tree' with an ax but when the hill is shown towards the end, the stump is taller then she is.
This depiction conflates ducking, a non-fatal form of public humiliation, with ordeal by water, a much more serious procedure which could be fatal.
King James walks gracefully and speaks upper-class English. The real King James limped badly from a childhood deformity and for his entire life spoke in a thick Scottish accent, which was further challenged by a lisp and a stutter. Ironically, Alan Cumming, who plays James, is himself Scottish.
The trial by ordeal is depicted a bit wrong by showing the person tied in a chair. In trial by water, the person accused of being a witch was stripped, bound and thrown into a body of water. It was thought that if the person was a witch who rejected baptism, the water would reject them and they would float. If they sank, they were considered innocent. Usually a rope was tied around their waist to pull them out. But some did drown.
Several English characters from the 1610s appear to be familiar with "Witchfinder General" as an official title. It was actually made up in the 1640s by Puritan activist Matthew Hopkins, who was the basis for the novel/movie Witchfinder General (1968).
Becka Savage claims to have found 35 witches, however, to identify potential witches, she used trial by dunking/ordeal by water. This involved submerging the suspect in water - if they drowned they were innocent, if they lived they were a witch. It is highly likely that all the suspects would have drowned, and therefore been proven innocent (albeit, dead). Consequently, Becka Savage had not found a single witch.