the loose link here is the family. i would shut that down entirely on email and phone. it is too dangerous for you to be the support for the sister.
starcat, please be careful. mine threw me down a concrete stairwell SIX MONTHS after i had moved out and gone no contact because he heard i was at a party. he left his job at the bar, came to the party drunk and insisted i leave and when i refused, he decided he would make me leave.