I've actually been to (and by) the site many times. Several of my mother's family have lived about 5 miles away off US 175. It is very sad to see and hear about the multiple vandalisms. Unfortunately, due to its remote location, there is little way that anything can be seen from the road (the point of the picture where you show the gate), as the memorial is about 1/4 to 1/2 mile away. It is an almost eerie area, and it doesn't help that the wind whistles through the pine trees--and that you may be there by yourself if you visit. The site not only shows a history of vandalism, but parties as well. I remember one that was planned while I was in college, by the time I got out there to see what was happening, someone had tipped off the DPS and they had the site blocked off at the turnoff. Believe me, I wasn't about to go out there at night. I just passed by; it looked like several were getting booted out by the officers. There are still locals there that care about the place. I remember my junior historians group in high school going out there one day (a Saturday? definitely a while ago) to clean up and do what we could. We trimmed grass, cleaned up the Historical Marker granite, dumped the trash that was overflowing in a nearby barrel that was full of bullet holes; plus I showed them the path down the hill to a creek for more water when we ran out of water to clean with. Back then, the Historical Marker granite was still upright, it hadn't been knocked down yet. It was sometime in the late 1980s when the land was sold (or given to?) the county Historical Commission for ongoing oversight. Not long after, the decision was made to add the gate and have specific hours allowed for visitation. Since I don't live in the area, I don't know how well things have gone with the addition of the gate and hours, but from the looks of your otherwise great pix, sadly, there are still those out there that would rather tear up stuff than take care of it.
I didn't realize till your pix that other members of the Killough family were buried over at the Larissa Cemetery. Don't know how much you saw of Larissa but you had to have seen some of it; it is community that most would consider a ghost town as it's heyday has long past. It grew and prospered in the late 1800s and had a college. As with many towns back then, Larissa was bypassed by a railroad (this one between Tyler and Jacksonville), and declined afterward.
It grew up around an old road (dirt road going northwest, paved road south to US 175) called the Neches Saline Road that pre-dates most area roads there; a Historical Marker can be seen on US 175 west of Jacksonville across from the turnoff to the road. Basically, the road was used as a path in the early 1800s between established settlements of the time (Nacogdoches, Fort Lacy) and a salt formation along the Neches River which is now covered up by Lake Palestine. The Neches Saline Road was the primary path of those that fled the Killough massacre; they were trying to get to the safety of Fort Lacy and Nacogdoches. Sadly, not all of the road exists now in a marked or paved condition but some of it can still be traversed.
Even though it's not a part of most national history books or school textbooks, the Killough massacre is still a very important part of East Texas history.
http://www.hmdb.org/marker.asp?marker=28129 (Neches Saline Road marker)
http://www.hmdb.org/Marker.asp?Marker=31698 (Love's Lookout marker, has some Larissa information)