Modeling and PX4 as controller in Simulation

Hello there!

I am trying to model a quadcopter and its dynamics, and I want to use a PixHawk as a flight controller, which is using PX4. I've designed and model of my quadcopter (so the dynamics are down), but now I want to test PX4 with my model, before I build it in real life. This is where my questions comes in.

1. How do I use PX4 as a controller in software only, no PixHawk needed? I want to see how PX4 as a controller handles my model in simulation, is there a way to do this?
2. When I've varified my model in simulation, I want to also do (as I understand it) software in the loop simulation, where I use a PixHawk controller and give it simulated data and see how it would correct my model, of course if it is possible I would like to aslo see how my drone model responds, how would I do this?

It is not clear to me from the given Matlab examples how to do this, so any help on this would be much appreciated.

Thank you in advance for taking your time, it is much appreciated!