How to model a Electronic Proportional Control Valve
You would use a linear regression curve for the mA vs flow rate for the selected with some 5 to 10 % hysteresis then multiple that curve gain above threshold by the input pressure curve with a linear constant if operation below 50% max pressure.

This is a 1st order approximation.

For better accuracy, modelling the exact part with Excel  curve fitting the range above threshold can yield a family of curves that can be used to compute the expect flow vs measured flow rate and then adjust for error reduction.  By always choosing to regulate on the rising current curve, you can avoid the hysteresis.



From testing, you may find that the threshold also shifts with input pressure, P so another coefficient on the threshold using P/25 {psid} to scale that threshold.

I do not know how to use Simulink, but the best tool is the one you know how to use.  I could probably model it in excel or even Falstad with a pot control, pretty quick, using Zener curves with a defined series resistance and threshold voltage for current and a capacitor with an AC sweep for hysteresis at some frequency with DC bias.

Example : Falstad