My reputation is too low to comment so I'll give some pointers in an answer :)
Looking at your design your structures weak points are the areas where the plate and the sensors interface, especially the ones in the corners.
This is because you have a very long lever from your load to the feet of your sensors and a very small contact area between the sensor ...
It's straightforward to model very slight deformation of the sphere (i.e., slightly flattening its surface). It's also pretty straightforward to model the case when the sides are already fully flattened and meeting at the corners. It's trickier to bridge the gap.
The small-deformation case has an exact solution for a single side (Case 2 here): the ...
There's a reason why they're called "factors of safety"
The answer to your question is in its title.
When designing a structure, we need to make sure of two things:
that the structure will remain a structure and not end up as a pile of rubble (i.e. that the structure is safe)
that the structure can actually be used as intended.
The first is easy ...