I just put in two ground loop isolators from Amazon for Comcast cable and that removed my hum. They were $19 each. They are placed right before the cable box and screw right into the input, then the cable line screws into the isolator.
The lack of output is most likely caused by not having the gain set high enough. The knobs on the front of the INUKE are not volume knobs but set the gain input for the amp. Unless you have turned those up all the way and found a lack of output, this is most likely your easy fix.
The gain should be set to calibrate the sub(s) to the main system, and the AVR usually handles this but you can do it manually with any SPL app or a meter. There's a lot of threads in this forum about setting gains, maximizing your system etc, but it all comes down to making sure the input level from the amp, and if need be, the AVR, are set properly. They are rarily too high in these setups its usually a need to turn it up on the dial knob on the amp itself.
If you have turned your main volume all the way up and on the amp only get 2 lights -- and feel the output it lacking, gain is definitely your issue. It's quite possible to not go past 2 lights and have enough output, it all depends upon the system and the room. But the key is you used to have it cranking and the setup currently is not allowing for that.