Well, Gang, after about 4 years of intermittent fiddling, I finally have my problem solved!
Donna of SOTA was correct when she said that problems like the one I was describing were nearly always a tonearm issue. I took my entire 'table to Mike of
austinstereo.com. He fixed the issue in a couple of hours.
Turns out the grounding wire in the tonearm cable had broken somewhere, so there was no real ground. So Mike snipped the old wire and created a new one. Additionally, he told me that the hum lessened but didn't completely vanish with the new ground wire, so he unmounted the Linn Basik LVX tonearm and tightened all the hardware, including some loose bits that help to ground the arm. That finished the job.
So, in the end, the issue had nothing at all to do with the Seduction.
I suppose I should mention, by the way, that I bought this arm used in 1986, so I guess I should've checked this first.
Many thanks to all of you who helped along the way!
Now to install the Russian Teflon cap that mingles sent me 5 years ago.
