We do not yet know what the complete specific structure is throughout the entire center of the Earth. Science has confirmed that there are liquids and solids within and we know approximately where they reside in relation to each other. We also know that the crust is floating on that liquid. As for the forces that allow that to happen, among other things like surface tension, the displacement of the floating crust overcomes the gravitational pull of gravity on it. If it had a lower displacement value, as in our rock example, it may very well sink and your suggestion of an Earth that had only oceans on its outer side might then be reality. However, we also don’t know if there is additional solid structure under-girding parts of the crust in a supporting role as well. There is obviously much for Millennial Science to discover about the interior of the Earth. We envision that the UM will give you and others the basic information to further the research through experimentation, observation and other scientific study methods described and used in the UM, as well as those methods yet to be found, to be able to find answers to more unanswered scientific inquiry.
As to your question relating to a mathematical formula on gravity that would “allow someone to see or plot” the massive global wide event of the universal flood, there were far too many different activities going on during that time, including significant widespread hyprethermal activity, to attempt to explain even parts of the activity in mathematical terms. Even if that were possible, the UM wouldn’t then be a book that could target junior high through the first two years of college level work.
We encourage you to continue your reading of the Universal Model and expect that you will find the answers to many as yet unanswered questions in your mind, as so many others have.