You will find the roof load rating is assuming the car is travelling @ 100k/ph with that load. Your adding 180kgs of load while parked and never intend to travel like that. The fact that you basically going to limit the roof load to your RTT, Your Rack and a Solar panel (that is basically irrelevant) i cant imagine your Patrol having a problem with the weight. There are PLENTY of Patrols, Prados, Hiluxes, Pajeros, etc etc,etc that have this setup. Dont worry to much about it mate.
Maybe play your nooky by ear mate, once you start using it if it all feels good let the feeling be goodIf your not wanting to push the envelope then maybe make a date downstairs hehehehe. But for sleeping they are made to do it. You should have no dramas at all.