Whenever I am dealing with an electrical problem with multiple failures, I generally try to look for a common denominator, such as power/ground. After a quick scan it looks like ECU-B #4 fuse in the engine bay has the potential to disrupt, power windows/auto lights/illumination/AC. As for the horn it gets it's power strait from the main fuse. Few questions below;
Any recently installed accessories? Poorly installed spotlights have been known to melt the wiring behind the dash.
Do the power windows work from the individual door switches?
Does the wireless door lock work?
Any other components noted not working? brake lights/tail lights/interior lights
Any lights/messages on dash? Charging warning light etc.