Water – Small soft spot on ceiling below shower

Joe, sorry to use the "answer" function again instead of adding another comment, I wanted to attach more pictures.

The tile I used was not available with a bullnose so I finished it flat on the sidewall. The edge cant be seen normally so I did not spend time making it perfect, but for your situation I retract my note about never finishing an edge with caulking. If you end flat to the wall around that corner it would be perfectly fine to use caulking for aesthetic purposes, use paintable caulk so you can paint a straight line down the whole side when you paint the wall.

Sorry I misunderstood your question, my situation was similar to yours and wrapping the tile around to the outside seemed like the best solution for me, and it looks pretty good that way (at least my wife did not complain, that's all that really matters).

This type of shower should not have bounce to it even it has foam underneath to give it a softer touch. The showers are more often supposed to be installed with a heavy layer of thinset underneath to stabilize the pan and to build up any voids. Some showers are a little softer than others but they don't bounce or flex... or they crack and break.

At this point you are asking us internetters what you should do. You are trying to repair it, you are thinking about products and so on. Well you can fix the crack with repair kits. However you cannot fix the flex that is causing the crack. So your repair kit will work until it dries out fully looses its flexibility and then you stand on the area again and it breaks. Maybe you notice a tiny rip... maybe you don't.

Use your resources better - your time and money. The base has to go - for sure. Not only will it be a lot less time to put a new base in but the big issue is the potential damage you are doing to the rest of your house. Water can slowly screw crap up and you don't want a small leak in places you can't see.

To answer your question - you only need enough slope for water to drain. I suggest that you give up on the pan repair and post another question around how you can get that pan out or alternatives for your situation.