If you can open the rear door, as in , the window drops an inch. Then your vehicle is detecting a park signal from the wiper motor atleast.
Are the relays clicking when activated? If yes, your fault is between there and the motor or the motor itself. If not, then test for feeds and earths at relay, to make sure it either has the signals to activate the relay and that the created bridge has power and earth each side. If its missing its signal , check the output from the module.
If the relay clicks but doesnt move the wiper. Remove the taildoor panel ; 4 screws at bottom and pull from the base upwards. Then check to see if your getting voltage there at motor, if no , check wiring. If yes , i guess motor.
Heated screen is just 2 wires, power , earth. With the above interior panel removed , check you have both. The missing one is the fault
(im sure you'll find a common denominator
)
I have no idea whats your fault , but get a multimeter and you can check everything you want easily.