What do you think happened to that butler Joo? Maybe the evil vampire killed him while trying to steal the gold. But, if that vampire did steal gold, then he should have been richer.
Ok, so when the senior detective died, where did those papers go that he had in his hand? Why are they asking Sanyoung to remember instead of directly going through his papers?
I don't think there was a 2nd sacrifice. The ghost is angry at kids, which I think means that Lee Mokdan was replaced with the elder daughter/girl at the last minute. That's also why the ghost kills 2nd child -- to show her hatred for how she died.