The setup is not clear to me: What exactly must be welded and to what, what are the moments, forces, distances involved, do all three loads occur at the same time? Pointing downward? How exactly does the fixation work?
The measurements are in mm's?
As I see it, it's a vertical jib with a horizontal boom with three pulleys (with each a point load), but with a hinge at the bottom of the jib?
A drawing in 3D, or with colors for the different parts in the assembly, might already help...