Does the intellitouch disable the control pad on the heater? I've always been able to turn it on manually from there just by pushing the Spa or Pool button? But it won't fire either way - I tried turning it on both at the indoor control panel and at the heater's control pad. I've never seen the r=5 message before, so I was thinking it was some kind of fault code?

It's not too uncommon to have different outlets in different rooms on the same circuit. It's possible that a connection came loose somewhere in this one circuit that serves all these affected locations, after verifying the power really is off, I'd start looking at the receptacle that the AC was plugged into. While it's unlikely with outlets in random bedrooms, look to see if there's a GFCI tripped somewhere if you've already assured yourself that all the breakers are reset.

Check if you are getting power to the fixture - remove the lamp from the junction box and measure the voltage using a multimeter. If you're getting ~ 120 V AC the fault is likely with the device. Otherwise, there is a switch/ some other interruption..

All I can say is, thank goodness for circuit breakers. And can you imagine what might have happened there if the circuit hadn't been properly grounded? Every metal box on the circuit could have become energized, along with every metallic appliance plugged into it with a 3-pin cord and plug. Someone might have been killed. I wonder if in some ways homeowners weren't better off back in the early days of electricity in homes, when many of them were afraid of it and therefore left installation and repair to the pros. The old cliche is that familiarity breeds contempt. I'd say it breeds carelessness.