Okay, new revelation.
I think any normal person would have given up by now, but being the curious person I am, I find it hard to stop troubleshooting. Anyways..
I took one of my car audio scosche line out converters (rated at 50rms), and took the high level (carries sub signal+power) wires and fed them into the loc, then took an rca cable, and used a 2-1 y-splitter and plugged that into the RCA sub input port, thereby negating the need to use the high level inputs on the sub.
Whataya know, doing so fixed the problem. No humming with my JVC amp turned off. Also when its off, messing with the sub volume knob makes no difference either. Out of curiosity, I put my fluke mutli-meter on the high-level leads, when off, my amp is not putting out any power on the sub channel(so that falsifies my idea that maybe it outputs a strange signal when off).
I know I cannot continue with my idea above however as it would destroy the amp.
Surely this has to be just a grounding issue. I just don't understand though why.