First, the efficient way for iip3 simulation is pss+pac. About your circuit, are you measuring out of band iip3 or in band? In other words, the f1 and f2 are in band or out of band?
It is good to have a look on the ports and qpss properties window of your test bench plus the result graph.
They do not cross. you are talking about the curves or the extrapolated lines? if the iip3 of your circuit is high, then the extrapolated lines will not cross till -10 dbm.
As you know, when plotting these two tones, by the method described in document, the simulator will give you the value of iip3. What value, do you get?