John Proctor uses the scythe incorrectly. A scythe is drawn right to left in an arc parallel to the ground. The stroke requires neither great physical strength or blade speed. However, Proctor, with much effort, uses a golf-like motion which rips what grass the blade makes contact with and arcs way over his head. The scythe is never lifted in either the draw or the return.
As John Proctor holds his confession note, the condition of the paper changes between shots from being almost completely crumpled within his hand to mostly exposed and barely wrinkled to mostly exposed but extremely wrinkled.
When John Proctor and Elizabeth are having their private conversation towards the end of the movie, his teeth look normal. However once they return to judge and Rev. Hale, his teeth look rotted and decayed. When he his hanged (the same day) his teeth are normal again.