Re: can't load the module
You need to follow the instructions in the log:
NVRM: rivatv was loaded and obtained ownership of the NVIDIA
NVRM: Try unloading the rivafb, nvidiafb or rivatv kernel module
NVRM: (and/or reconfigure your kernel without rivafb/nvidiafb
NVRM: support), then try loading the NVIDIA kernel module again.
NVRM: No NVIDIA graphics adapter probed!
As you're running Gentoo, I assume that you'd know how your kernel was configured.