Does this bolt directly to the factory rear bumper?

Yes, it's designed to mount at existing factory attachment points on your Grand Cherokee rear bumper. No drilling or frame modifications required.

Will the chrome finish hold up to road salt and weather?

ABS with chrome plating is built for outdoor exposure, but regular rinsing in winter climates extends the finish. Avoid harsh abrasives when cleaning.

Can I use this as a step to load cargo onto the roof?

The step surface is designed to support your weight for loading and accessing the rear area, but always verify it's tight before putting full pressure on it.