Take a shifting spanner, I've encountered weird sizes (12mm bolts/imperial sizes) when tightening nuts.
As for a general rule of thumb, if it is an expansion bolt that has been properly set, it only requires the nut to be tight enough to stop the hanger from spinning. Experience could replace a torque wrench
Oh and as for SCC, the actual type of bolt and material would be the main factor in determining whether the bolts would be subject to SCC: Rolled vs turned bolts (all the bolts that have failed in SA were the turned ones, stainless 304 - problem is it's not easy to tell which are which after they have been placed, unless you are familiar with the specific bolt brand/model in question)
Other factors include: How far are these bolts from the sea? Prevailing winds? Relative humidity? Is the limestone the same type of aggressively corrosive one found in southern Thailand (from the location it looks like it).
The ARF has interesting info about this. http://www.climb.co.za/anchor-replacement-fund/
And if they are loose glue-ins, well then
watch out for dodgy fixed ropes as well, a girl in Ton Sai fell an entire pitch after sitting back in her harness clipped only to a fixed rope used to access an upper tier crag. She was nicely caught by jungle and survived.