Grounding amp..., trying to ground my amp Options

[6gsillyca]

I posted a while back with problems i was having with my subs, they were sounding wierd and realllllllly distorted. anyways, i got it fixed. it was a bad ground, the friend that was helping me wire up my system used a U-terminal, instead of a ring, and just screwed it in there. i went back and rewired it to a 4G stinger ring terminal (with the rubber condom on end), drilled a new hole and sanded down and screwed in.

now...problem

it started acting up again last week, so i had a look at the ground and to my amazement it looked like sh!t. the rubber around the ring terminal was all melted, the 1" foam under the carpet had a hole burnt up to the carpet, and the metal i sanded down was all black. i tried to clean the metal and re-screw it down only to find the hole was stripping...

-why is my ground get like this? do i need to get 0/1G wiring for ground?
-is it normal for the rubber thing to melt?
-how can i get the screw to stay in, without stripping, but still getting it nice and tight?

system is 1200W amp and (2) 500W rms/900W peak subs

thanks