I'm really at a loss. It should be working as far as I can tell, unless you do have some sort of problem with your XF86Config-4 that I'm not spotting. The only thing I can think of to suggest is to go to the NV forums and plead for help:
There are a few people there that really know what they are doing if you are lucky enough to catch their eye with a detailed post and subject.
Place to discuss Debian Linux and Debian based distributions