Although Buford Hazlitt is revealed here to be Seth Hazlitt's cousin, his brother Mark is stated in "Curse of the Daanav" to be his only relative.
The white Mercury Cougar seen at the beginning when Jessica and Seth were driving and lost had a California license plate.
There's never an explanation for how the fake nail ends up in the victim's hand, or the package of fake nails ends up in the trash.