She lives! It was plain, old, uncomplicated, simple RFI. Clipped two ferrite beads onto the coax, and another two onto the USB cable, et voila, JS8 and WSJT-X work just fine. Thank you to everyone who contributed help and hints, and I apologize...an Extra really should have known better!
Side note to anyone who wants to use JS8Call, reduce minimum samples to 1 from 480. I don't know if the rise and fall thresholds really make a difference, but 10 minutes of playing around this morning before work led the to reduce those numbers from 80 and 60 to 60 and 40, respectively...it seemed to make the radio "hear" what had previously been a blank waterfall. Made a few contacts after that before my paycheck called to me...
73, see you on the air!
