I'm tackling the most egregious noise first, and that would be the S8-9 noise across the 80 meter band with 60 Hz hum.
To get a better idea of when this noise happens, I tuned my receiver to a frequency where the noise is loudest, and started recording it in Audacity on my PC. I started it this morning, and will stop it tomorrow morning at the same time. Just looking at the waveform in Audacity, it's pretty easy to pick out when this noise starts and stops, which I hope will prove helpful in locating the source.
Tonight I turned up the volume on the rig to see how loud the noise was, and it was S8-9. I took another walk around the neighborhood with my portable Sony shortwave receiver, like last night, but was a little more thorough on determining the boundaries of where I could hear the noise, and it's definitely coming from my next door neighbor's house. I noticed that the noise is extremely loud right at the south end of our property, across a fence from their garage.
Since the Sony receiver was getting overloaded when I was in that "hot zone" on the south end, I needed something with an attenuator. My little Yaesu VX3R handheld radio is a terrific miniature VHF/UHF handheld, but as an HF receiver, it leaves a lot to be desired. In this case, though, it was a help - sort of like having an HF receiver with an attenuator you can't turn off! It happens to have just the right (lack of) sensitivity for this task, and it doesn't really register the noise until I'm a foot or two from our fence, and locates the noise source laterally along the fence. Whatever it is, it's coming from my neighbor's garage, and there are a couple of boxes mounted on the exterior wall of the garage that might be the source.
Now that I'm pretty certain about this, I'll stop by and ask to poke around a bit (we have a good relationship with our neighbors).
This RFI sleuthing is sort of fun...