Some educated comments...

RANRAP:
Early self-protection jammers needed a 4 second delay to tune-in in the signal PRF. This could be exploited in two ways:
1) cycle 75km/150km switch: false targets jump in range, while true target remains on the same range mark.
2) turn ant/ekv off/on: true target dissapears, while false targets remain.

Early AN/ALQ-131 jammers used VHSIC - Very High Speed Integrated Circuits, basically a digital processor with 1MHz frequency (cutting edge technology during the 70's)...
... our adversary will have much better ones, so the techniques mentioned above, will simply not work.


3) IIRC, S-75 also had a variable PRF ("Peremennaja Chastotota") mode, which could make false targets drift in range and that would be noticed by operators.

Peremennaja Chastotota is actually modelled in SAMSIM, but it would not help against RANRAP, for similar reasons, mentioned above...


ANGLE JAMMING:
3) In later generation S-75 Volkhov and S-125 Neva, the GshV and GshN modes were introduced. It provided the filtering of angle jamming and sidelobe blanking, reducing angle errors further or negating it completely at much longer ranges.
Unfortunately, GSh modes were implemented in a very cheap way, and they were NOT compatible with SDC against low flying targets or targets in chaff clouds...

Hmmm...
... SDC works by amplitude subtraction of consecutive reflections, while the GShV is based on the logarithmic subtraction of the signal received by two antenna systems.
I cannot see, how could this task be done in an expensive way, thus GShV + SDC could work in parallel.


RANGE-GATE PULL OFF:
2) In GshV and GshN modes, S-75 and S-125 had a built-in capability to track on leading edge only in range (I've seen this mentioned a couple of times in GShN and GShV design and field test bulletins).

False target is introduced a before the real target, before it is pulled off...