I have had a look and a think. In answer to your basic question
How could I wire this so that I keep the on/off functionality of the wall switch? I am aiming to be able to use either the remote switch or wall switch independently.
The answer is not at all easily.
First of all, if you use that AYK048 device, to purely operate the light, it will need to be powered from the lighting circuit, not from a wall socket.
Secondly, I guess that, if the light is on (from the wall switch) you want to be able to turn it off from the bed? That box only has make contacts, and you would need changeover contacts, so you would need a mains relay that has changeover contacts.
Even if you could engineer and achieve that, you would then need a 3-core and earth cable running to the light switch from the AYK048 (or perhaps the light fiting, depending on how your wiring is done).
That seems like an awful lot of work, and wiring. Have you thought about having a bedside light?
More seriously, you could replace your wall switch with a remote control dimmer like this
there is a remote pad that you can buy for a fiver.
You can then operate the light either from the doorway, or from your cozy bed. AND you can get romantic by dimming the light!! Job done..