so you suggest to follow fig. 4 of the datasheet, to shield capacity and impedance of the cable which gets too (radio) noise?
I would try it.
is it ok in your opinion to add the resistor and capacity close to the sensor, such as in the following sketch: attachment Untitled.png ?
Yes, that's how I would try it. Although the the datasheet suggests it only for heavy capacitive load, it damps the noise too, so you should get a more stable reading.
In the "Typical Applications" of the datasheet in most cases they use a shielded cable. Is your cable shielded? From your circuitry drawing I would read you're using standard cables without shielding or twisted pair.