brake rotor is loose

[aaronng]

i tried tightening the bolts, tightening the screw on the rotor although it keeps coming back when i slow down it makes this screechy noise although i have alot of meat left and this is even when it heats up, and when i go to slow down instantly it sounds like the rotor makes a clunk and a piece of metal scrapes againts my brake pad as im slowing down.

the rotor moves independently just slightly forward and backwards

That's odd because the screw on the rotor should prevent any rotational movement of the rotor. Could you check if the center bore of the rotor perfectly matches up in size with the centre hub of your S2k?