Passive low-pass filtering question for a transducer output
Assuming that the output of the instrument (used as a sensor) has some really noisy pressure input and the internal instrument workings do produce this kind of jumpy output, the answers are:


Yes, a simple RC filter with 1kHz cut-off is an acceptable solution
Yes, the data show that this is good enough;
Most likely reason for the ringing at 1kHz is a flaw in instrument's design of output stage of internal DAC. The 1 kHz ringing cannot be explained by cable/load mismatches.


SIDE NOTE: It looks quite obvious that the selection of this sensor is inadequate to the nature of input pressure signal. The instrument states "settling time" of ~0.5s, which limits the spectrum of input signals to pretty much static pressure levels.