Contractors did faulty Silicone caulking job along shower door, causing wall to be damaged by water...Wondering how to fix wall, and put tiles back on....Wall basically became a sponge....where to start?

have recaulked area, now would like to fix area that was damaged....any tips would be greatly appreciated.....

{we do live 1 mile from beach in Southern California, So i'm thinking some of the bubbling paint could be caused by moisture in the air, contractor speedy paint job in bathroom, or maybe it is all caused by faulty caulking job (basically noticed needle sized holes in silcone caulking)**

here's some pics:

this is pic of other wall next to shower it leaked there also, but not as bad, wondering if i can just sand wall down a bit and replace tiles to it?

For wall behind toilet, I imagine i have to remove toilet, cover whole in floor from toilet, not sure if i can just sand some of the bubbling paint, to smooth wall again, possibly pick bad parts of wall out and use some sort of drywall putty to get wall looking right again, or do i need to cut wall out and replace drywall?

will possibly be selling lot the house is on in near future, and moving so it doesn't have to be picture perfect new this new that.....but would like to get it looking better than it is.......thanx for any help........