Hello and thank you for your tests!
Of course, as you say, this is an early preview, an alpha 1, so we can and we will improve the software. With the understanding the the highest security level is reached only by renouncing to traffic splitting or by splitting traffic only through boosted virtualization via a proper hypervisor, our solution aims at offering a fair balance between a very light implementation and a safe environment. If we pushed on virtualization too much, then the user might as well use directly pushed solutions of non-Linux third-party components and software suites, such as VirtualBox or Docker. It's not in our vision to burden the AirVPN Suite at those levels, as the Suite is thought to remain the most lightweight piece of software we release.
In the current default setup, you have a minimum of two separate login users in any Linux box: airvpn and your usual user. By default, only airvpn can run cuckoo. If you consider not to add your current user to the airvpn group, you can safely rely on the fact that the types of processes you mention launched by your current user will never be affected by processes started by airvpn user and vice-versa. In this way it's almost impossible to cause a confusion by distraction and, for example, using a browser outside the tunnel while you think that it's inside.
It's also obvious that a decent concentration level is always required, but that's required even with full virtualization, because no security model can save you from the distraction to assume wrongly that a specific VM is connected to the VPN while in reality it is not. So nothing new, traffic splitting was, is and will be requiring some attention, no matter how you achieve it. Stay tuned for the alpha 2, we are working on it.
Kind regards