Toxic Parents are a reality, I don't know why you can't tell the truth about a horrible past in Dramas People are more capable of handling the truth (that your bio father is a psycho killer) with the care of friends and family. Any sane mother or adult would have told the SFL truth about her father considering the harm her dangerous obsession of meeting with a killer could bring.
I can't seems to imagine how they can drag it to 20 episodes. With all the secrets revealed it should end in 8 episodes more than that would be a painful drag.