Sounds like your having re-radiate issues with the power lines in your house. It’s common for wires, cranes, long metal things to re-radiat transmissions from antennas and transmitters. Not much you can do about it other then try to ground it out by a shielded wire run or filter it out with specific filters in your power supply. Not seem much for home use as it’s not usually an issue but check industrial safety sites and you may find something for the frequencies you have measured.
One other thing your not using an internet expander that utilizes your power wires as that dose put other frequencies on the power line.
One other thing your not using an internet expander that utilizes your power wires as that dose put other frequencies on the power line.