Twin Suns Three
Your mistake was that you asked around, instead of going directly to the source. You should have asked your sister if she had dropped out, not other people. Now, your sister has to deal with outsiders confronting her about supposedly dropping out of high school and breaking a promise to a dead sibling. Of course she is going to be angry and take it out on you.
However, everything after that is on her. SHE needs to act like an adult and quit unblocking you so she can send threatening and insulting messages, then re-blocking you again. That is childish. She needs to grow up and own up to her actions. If she dropped out of high school and broke a promise, then she needs to admit that to herself and accept the consequences of that decision.
YOU on the other hand need to ignore her and her father. For the most part, that has been taken care of. She's blocked on Facebook so she can't send you any more messages. Keep it that way. Even if other family members or friends try to tell you that you should work this out, keep her on that blocked list. The same goes for the phone number.
Keep the text messages on your phone. They can be used as evidence in getting a anti-harassment or restraining order. You don't have to know her exact address. The police will handle that. You just need to present the evidence that she has been harassing you, that you've been threatened with violence, and the rest will be handled by an investigator.
Well here's my thing. The only reason I didn't ask her was because she had me blocked on Facebook and I didn't have a way to get a hold of her otherwise.
I actually talked to a friend of mine on the local police about the whole situation and she said there isn't enough evidence since Facebook erased the stuff she sent to me after I reported her for harassment. BUT she said if she continues after this whole mess (and make it very clear that I will do this if she doesn't stop) to go to the police.
Which is what most people here are telling me.
Thanks for the help!