I don't know if this is possible, but can a door family read the rating of a wall and also have it read in the door schedule? I have tried applying a shared parameter on the door family and adding it in the project. I am not understanding how I can link the two together. Please help!
No. That relation wall-door in regards to the fire rating is not available through parameters in the way that you have described. A common solution is to handle this via visibility graphics, as a way to have a visual control of the fire rated values of doors and walls.