The coordinates to Big Schloss are accurate but the map displayed by the TopoZone link is not. In fact, it's not even close.
Big Schloss is an out of the way area. It doesn't see much traffic. The only area I have climbed in is north of the wooden bridge (it's the only one) and facing to the west. Watson's climbing guide describes about a dozen routes but we've never been able to locate them from his sketches. I don't know the technical name for the rock but it's very abrasive.
Some of the routes may be leadable but I've always stuck to top rope out here. I recommend belaying from the top and rapping to the base of the climb.