"And if she does not? If we are wrong, and she she overturns all we have done? Us included?"

There is the hint of fear in how Norrell asks it, but also something in him that is desperate for reassurance from Coward. For him to tell him that it will all be fine, that there is no threat to worry about. Even though, in truth, Norrell will still worry regardless. To hear it said still soothes even if he does not believe it.