That's quite hot. My AC56U hovers at around 72C here at the same clock. I have no idea what's a normal temperature for the AC68U however.
I'm not sure whether the temperature reading is correct, now I am back at stock, it is 90 degree celsius.
However, physically it is that hot(two hands covering the front and back of the router). Thus, the readings may not be accurate at all. Well, I'll try again tomorrow then.
But is it okay to overclock both CPU and RAM freq(1000MHz and 667MHz respectively) ?