JFET-Transistor output characteristics in PSpice
You can try to adjust various parameters in the .model, but in the end you have to remember that a SPICE element is only an approximation of the real-life counterpart. You can clearly see that the saturation region is a straight line in the simulation, and the knee points are rather abrupt. Getting a perfect match with the datasheet is quite impossible. Besides, the JFETs are known to have very large variations even compared to their own datasheets. It's one of the reasons you don't see constant current generators with JFETs everyhere. BTW, you used 0...-4 for the Vgs, but in the datasheet it's shown as 0...-1. For this case, you could try adjusting the beta parameter. In LTspice, beta=3.5m seems to come closer to what's shown (the default value is 4.682m).