The blu tak should decouple the speaker from the room.
Biwiring shouldn't make any difference to your bass response. You should try putting the pins back in between the terminals of your speakers as an experiment to check whether the tweeters are connected correctly. If I were you, I'd do this as my first check.
Banana plugs also won't make that much difference. They're a convenience as much as anything and some people prefer going without (for instance 47 Labs and Mapleshade suggest not using plugs with their speaker wire). I've tried a number of different types and in my experience, it's only really the Eichmanns and a few of the very esoteric ones that made an audible difference for me. I didn't have so much success with the QED airlocked ones. In general, bare wire cleaned regularly with Brasso is good enough.
Try the other solutions on that list I gave you - Bringing them away from the wall and stuffing the ports and see where it gets you.
I'm assuming you're using speaker stands is this correct? Using them on the floor or on a shelf may cause you some problems of this nature.
8.2 aren't that bassy.