dilivion

There is nothing to imply that there is something to be discovered at that energy scale (100 TeV), and likely any potential breakthrough is far from the reach of the FCC. At least the LHC was aiming for the Higss (which could also be discovered at the Tevatron, but this was not certain at the time) and there was a great hope for supersymmetry. Perhaps the funding would best be used in other endeavors…

The discovery of the Higss boson and nothing else outside the Standard Model at the LHC is the worst-case scenario: we now have a theory of everything that predicts nothing...

To understand the strong force coupling look up the concept of asymptotic freedom.

This running of the coupling constant would in principle allow unification with the electroweak force in most theories e.g. supersymmetry - we just have not worked out the exact framework.

The particles are steered round the accelerator with magnetic fields from superconducting magnets.

Higher speeds (and thus energies) can be achieved by increasing the circular circuit radius by limiting the force that has to be applied and the energy loss in the acceleration (change of direction around the circle).