This might not solve your issue, but regarding the aperture control lever, you said:

2. broken aperture control apparatus.

 

i can't find any way to verify if in fact my camera body has some broken aperture sensor.

Nikon bodies have a physical lever that mechanically operates the aperture in Nikon lenses (all lenses except the relatively recent "E" lenses that have electronic aperture control. Your lenses are not E lenses). The "broken aperture control apparatus" is not referring to a sensor, but to the aperture control lever in the Df's body, as shown by the arrow in this image:

Nikon's support article, Why is my DSLR camera consistently over or under exposing?, shows what a bent aperture control lever looks like, and possible damage done to lenses' aperture control linkage due to improper mounting.

This might not solve your issue, but regarding the aperture control lever, you said:

2. broken aperture control apparatus.

i can't find any way to verify if in fact my camera body has some broken aperture sensor.

Nikon bodies have a physical lever that mechanically operates the aperture in Nikon lenses (all lenses except the relatively recent "E" lenses that have electronic aperture control. Your lenses are not E lenses). The "broken aperture control apparatus" is not referring to a sensor, but to the aperture control lever in the Df's body, as shown by the arrow in this image:

Nikon's support article, Why is my DSLR camera consistently over or under exposing?, shows what a bent aperture control lever looks like, and possible damage done to lenses' aperture control linkage due to improper mounting.