Are you denying Newtonian gravitational attraction now? Saying that it has not been observed only calculated?
Do you know how many assumptions are built into those calculated values? The theory has formulas, the formulas have factors, the values of the factors are assumed so that the formulas fit the theory fit the observations.
When those values don't work out, 'dark matter' is invoked or 'large iron cores' or Saturn being 'lighter than water' as necessary.
Try this. Assume that Saturn has the same density as Mercury and see if your gravitational calculations 'work'. They don't. The values are forced into the formula into the theory to fit the observations.
Not that you understand any of this...