The usual fault for no instrument cluster lights is the rehostat that controls the intensity of the lighting.
Sounds as if your other problems might be a bad main ground to the cluster. If you can identify a ground point on the back run a temporary ground to check. You also may want to check the fuse but my suspicion is it would have not become erratic if it was just a fuse. Although it could also be out now as a result of whatever is wrong.