Until now I did not find the solution to extract directly the internal stress of the beam, as well as I am not able to find the forces/moment that act along the length of the beam.
Fortunatelly, about the loads at the end of the beam I find a solution. Using two "weld joind", one for each beam end that connect the beam to the other elements of the structure, I am able to extract the forces and moment that act at the ends of the beam. In particular I use the "constraint forces" and "constraint torque" signals.
[EDIT]: I developed a usefull Simscape library that give you all the information about your beams (forces, displacement and even Von-Mises stress and strain)!!
See this link for the BeamStressLib repository.