One thing I left out of my post on this topic quite accidentally is that the home has changed owners over the past 8 years. I don't think it's something specific that either owner has "plugged in" but there's definitely something in that house that's causing a buttload of interference. Would love to have the local power company get there and inspect the electrical service and see if that's what's causing it, but neighbor not open to that for some reason.
Of course, the FCC has been no help.
Grab a small portable AM radio and walk around your property and the immediate neighbors. I’ve found interference inside my compound using a portable. Many times that same interference will show up on the AM band, with the closer you get to the source, the louder the interference. Dimmers switches and certain Chinese LED lights are many times the culprit of interference. And Plasma TVs give off enough RF to give one a sunburn. Those things are just nasty.