Keep trying. Contact the local media in the Sumter area. That would put some pressure on law enforcement to respond, if they face negative scrutiny from the same newspapers and television stations that praised them for pursuing the case for 45 years to identification.
I never got my hopes up toward an arrest. But it is outrageous that law enforcement is not displaying basic courtesy to family members.
You might try contacting the daughter of the former sheriff, the guy who was in charge of this case from the outset. She was interviewed when the names were revealed, emphasizing how much the case meant to her father. Somebody like that could jolt the current sheriff into some sense and decency.
Use a tag team approach. They might ignore one family member. But if multiple brothers/sisters -- or whomever -- continue to contact them, they'll get the hint that this isn't going away and they need to respond.
I'm not sure if the Buckley and Freund families have made contact. That would be even better, if law enforcement is being approached by family members of each victim.
This case needs to be covered by one of the major networks. Tonight I was watching the Cali-Doe case examined by the Paula Zahn program on Investigation Discovery. Those programs rely on cooperation from law enforcement. Many investigators love national spotlight like that even if they typically are not media friendly.
Members here have pushed various programs to take a look at this case. Family members should not shy away from that. Don't allow anyone in the family to embrace the fearful aspect of an examination like that, compared to immense potential benefit.