Re: Install = Success, SaX2 = Problem, startx = Crash
You've got a seriously broken config there, you might want to clean that up a bit after your problems have gone. ;-)
Anyway, there are two things that you need to fix.
First, most importantly, you appear to have problems with the nvidia.ko kernel module. I guess that you do not have the correct entries in /etc/modprobe.conf (or /etc/modules.conf, depending on your kernel version) -- check the Nvidia README for that: you should stick an alias for the nvidia module in this file. Also check whether the Nvidia devices exist (/dev/nvidia*). This will enable automagically loading the kernel module when it is needed.
You can see if you have the kernel module loaded by issuing the lsmod command, if it is not loaded, you can load it on the spot by entering 'modprobe nvidia'.
Your second problem might already be solved now. Your X log states that the GLX extension could not be loaded. If this error persists after the first fix, check whether you have the correct extension in /usr/X11R6/lib/modules/extensions (remove or move the libglx.a module if it's still there). Furthermore, Nvidia depends on its own libraries in /usr/lib/tls, check whether they have been properly installed.
The README provided with the driver is stuffed with details, consult that if necessary.