If you can determine who owns (or owned) the cemetery, you might be able to track from there to a record of who was buried there. Possibly a local individual or historical society may have kept an old record. Another way to find information would be to scan historical newspapers that covered the area. Descendants of founding families can sometimes lead you to old sources of information. Check for any local written histories. And also deeds for the land itself (at some point cemeteries started giving deed to folks who bought grave plots).
As for the deteriorating headstones, from what I've read so far, there aren't many ways to preserve a headstone that is in bad shape. If you can afford to, placing a small bronze grave marker might be an idea.
More importantly, photographing the existing cemetery grounds and points of reference nearby, along with getting latitude and longitude coordinates, and publishing that information along with knowns burials is another way to preserve the history.
Here in the States, county governments want to know where cemeteries are in case someone wants to develop the area.
I'd encourage you to turn over every leaf you can think of. And once you think you've done it all, go back over everything from the beginning and see what else might point to another source.
Ground-penetrating radar and other technologies can help identify where something is below ground, but can't to a thing to determine who's buried there.
Best of luck to you!