Still not able to figure out the final circuit. I am going through some of the other threads to design. I can then post it.

 

Forget about trying to build a simulation model for an RS485 driver with discrete components like 2Nxxxx or BSPyyy. The output drivers of RS485 drivers and many other devices are designed by experienced semiconductor designers who have the possibilities and knowledge to adjust all the parameters of the output transisors/FETs like gate length, gate width, numbers of transistors in parallel, bulk supply, protection circuits etc according to their needs. Discrete off-the-shelf transistors have totally different requirements.

Look into the data sheets of a driver and you will find parameters like open circuit output voltage, minimum output voltage under defined load conditions, output signal rise time and so on. This way you can build a behavioural model with simple pulse voltage sources with internal series resistance. These simple models are much better than any try with discrete components. More than two decades ago I used this approach for simulating a professional RS485 tester.

And keep one thing about simulation models in mind: This is only simulation not the real world. No model is perfect, not even the models semiconductor designers use.

Try to estimate: How good is your model for the desired problem? Can you accept the difference between your model and real life?