first of all thank you so much for your kind help and patience
You probably already know this, but when you hover over the colors highlighted above you see (+ & -) on left side, just press + till you see more color gradients. This improves understanding of the solution for me. Try different options like show contours or bands to see more variations or maybe 'drag aqua color band down towards 0'. Isolines help a lot too.
Actually, I had forgotten about this function. I will treasure this advice from now on!
1) I am wondering where exactly is Point mass located. (If it is shown in Red color in left fig, exactly over frictionless support or is it same as you previously mentioned, quite far away from fixed support.
The point mass is located quite far away from fixed support. The part highlighted in red on the shaft is where I decided to apply the load due to that mass. Basically, it is equivalent to applying a remote force. Or am I doing something wrong?
2) As you said, not a cantilever now, how are you hoping to load the pin structure ?
Perhaps the case of "simply supported beam" could be more truthful, but I'm not completely sure. Now I try to explain better what the problem consists of, so maybe you can give me some advice about it
Can you please tell what condition is it ?
My problem consists in dimensioning the shaft and the support system of an automatic positioner (similar to that for welding by robot) on which a workpiece is keyed and that must be worked according to different angular positions (in fact I think that I should add to the model also the centrifugal force due to the rotation of the point mass).

As you can see from the figure (or at least I hope you can see it) there are two pins mounted on two mobile turrets that have the task of supporting and transmitting the rotary motion to the workpiece. Therefore, as previously mentioned, in reality the pins are not constrained in the direction of the rotation axis and are held in position by an axial force exerted by a linear actuator placed at the base of the mobile turrets and which counteracts the axial reaction thrust that the specially-shaped shaft exercises on the two pins.
To simplify the analysis, I decided to exploit the symmetry of the problem and therefore to analyze only one of the two shaft-pin couplings, thus halving the value in kg of the point mass.
In addition, I have tried to constrain the problem as it is in reality but, working in "static structural", the model is under-constrained and unsolvable. Because of this, I replaced the thrust force exerted by the linear actuator with a fixed support. In this way, going to check what the value of the constraint reaction in the axial direction is, I can calculate what the thrust that my linear actuator must supply to the turret must be to avoid the disengagement of the shaft.
I hope the problem is clearer now. If not, do not hesitate to let me know and I will try to provide you with further details.
Thanks again for the help!