Complex sentence: Rev. Parris is also trying to get them to confess, but that is because he wants to save his own life: since the trials began, Parris has received some not-so-subtle threats to his life.
Split into simpler sentences: Rev. Parris is also trying to get them to confess, but for a different reason. Since the trials began, Parris has received some not-so-subtle threats to his life.