Get yourself a baking dish and fill it with water. Next, take a coffee cup and fill it with something so that it will not float in the water of the dish. Seal it off and then place it in the dish. Make sure that the cup is tall enough so that some of it juts above the level of the water.
You now have a model of the earth. The part of the cup jutting above the water line is "dry land."
I think this model is incorrect. At least part of the "land" is deformable. Mountains rise and fall over time. If your cup can be deformed then it can be flatten out and under the water.
As noted your calculations for Everest must be out of wack.