Torque from the engine is increased by the gearing in the same proportion that speed is reduced.
130 N*m of torque is 95 lb*ft. A 250 pound clydsdale like me standing on a 170mm (6.69 inches, or .558ft) crank, with a 2:1 chainring:sprocket ratio (52 gear inches on a 26" bike) would apply 69 lb ft of torque to the hub.
When the hub is operating at less than 1 gearing (a reduction) all the output torque that is not supplied by the sprocket has to come from the axle, and that axle must have something to push against, hence keying it to the dropout.
Note that this same applies to coaster brakes, which depend on reaction arms to handle the torque, not axles keying into the dropouts.
So is there any good way to add a reaction arm to the hub? Possibly you could cold set the stays a little wider, and add a steel arm that picks up the keyed axle?