I totally agree with you on Mansfield Park but haven't seen the others. I can comment on Catherine's reading material. Andrew Davies apparently has her reading the The Monk which certainly was dodgy. John Thorpe read that but not Catherine. She read Udolpho which was unobjectionable in the extreme, apart from mysteries and general gothic horrorness. Lots of almost seductions but nothing really graphic. The point JA makes is that Catherine really isn't reading anything bad but John Thorpe is. Davies seems to have missed that point.