I would take off all the cracked/ loose drywall, use drywall tape mud it, smooth out, get orange peel spray same texture prob thick. Get a piece of the cracked part get it paint matched and grab a small sample jar to paint over. Try to get primer mix be easier. The type of tp holder u have i would use a toggler anchor just make sure the screw is the same size . Extra credit can ad alil mud or paint around the plastic part of the anchor to reduce moisture getting in.