Xorg configuration

How did you generate xorg.conf? Manually or with nvidia-xconfig? Did you try startx without any configuration?
[ 32.352] (II) NVIDIA(0): Validated MetaModes:
[ 32.352] (II) NVIDIA(0): "NULL"
This usually means that the nvidia-modeset kernel module is not loaded.

Quote from x11/nvidia-driver's pkg-message:
Starting with version 358.09, some important functionality of the driver
has been broken out into a separate kernel module, nvidia-modeset.ko.
Users that experience hangs when starting X11 server, or observe

(II) NVIDIA(0): Validated MetaModes:

in /var/log/Xorg.0.log should replace ``nvidia'' with ``nvidia-modeset''
in their /boot/loader.conf or /etc/rc.conf configuration files, depending
on how they prefer to load NVidia driver kernel module.