curing the rock in RODI won't work. The bacteria you need is saltwater based, not freshwater.
I'd kill the rock by leaving it out in the sun for a couple of weeks, knock off the big dead stuff, then put in your tank aquascaped the way you want, add saltwater, add bacteria in a bottle and let the cycle roll. It should only take a week with the bac in a bottle products.
Starting all over i mean in terms of the tank. Dead sand, dead rock.
Ah, no new tank. I moved everything over to the 125G a couple weeks ago. SO I am dealing with adding rock to an existing tank. I have 100lbs in there now, thought to add 25-40 lbs of the rocked cleaned to the tank. Sounds like everyone pretty much sticks to only adding live rock to an existing tank, not adding dead rock.
The thing is, you could clean it, but you won't know how much is left on the rocks in the "impossible to get to" places. That stuff is going to endup causing a nutrient cycle.
You could always set the rock to start curing for a week and see if it ends up boosting the Ammonia or Phosphates in the container it is curing in.
The the amounts are low enough that you can live with them then you should be fine. Just be vary careful with that.
-The nutrients are going to be more concentrated in a small container so take that into consideration. A 60 gallon container would show an an increase of nutrients that would be 2 times as much as a 120 gallon tank.