All of this damage is repairable. Here's a list of things you will need to do;
1- Kill the mold. Use a 50-50 mix of bleach and water in a spray bottle. Spray all areas that have mold and allow to dry. You might have to spray these areas twice. The mold will turn white when it is dead.
2- Stabilize the wall surfaces. Prime everything with Kilz or similar primer. This will seal and glue the drywall paper. Allow to dry overnight.
3- Lightly sand everything with a pole sander and 100-120 grit sandpaper or sanding screen. Look for additional loose paper and carefully remove.
4- Patch the damage by skimming a layer or 2 of drywall mud over all the walls. Tape any large cracks and open seams including the corners. This is where the most work is. You can sand all of the walls after a coat or two of drywall mud.
5- Texture will be needed as producing a smooth wall is difficult, even for pro's. The easiest are orange peel and stomp brush. Both of these can cover up a lot. The sand texture will also work but will need a better smoother wall to start.
After all of that prime and paint.