Hi Alex,
Thanks for the file.
I adjusted first the number of segments on the sphere, then the Spline interpolation.
This gave a less dense result.
The Boole was set Single Object> None.
Then the Current State to Object was used.
The resulting Sphere Cut was all I was after. Points too close to each other are treated with the Weld Function.
The Sphere surface was then extruded on edge. In a few small steps.
The last one very small (0.01) and then moved along the Z-axis to create the volume. The Z value [size] for this selection was then set to zero to make it flat.
A few extrude steps to create a solid edge and Fill Polygon Hole to finalize this step.
The N-Gons left on the surface were handled with the Spline Edge and Knife Tool.
After all, a short Optimize function was used.
The SDS (subdivision surface) works now reasonably good. A CAD precision can’t be given here, as the would require a mathematical approach, as given in most CAD apps, and the precision is then broken when you go into polygon mode. I will not even pretend or motivate expectations into that direction at all. But I you know that of course.
Here is the file back:
https://www.amazon.com/clouddrive/share/jsEAfeZTxyXeZbXUMCpq0nzKWr0WiugXtoLDn4gTaYe
Screenshot
https://www.amazon.com/clouddrive/share/Vkams6skX3vAEgl1zXQ9aq4c0LhePQQW1uOmIARs9LF
All the best