Wthout looking at anything else I found a error under your graphics device section:
You have End Section left uncommented out.
# VideoRam 256
# Clocks 25.2 28.3
# Device configured by xf86config:
You did not start a section but are tring to end one!
This could be causeing X not to read the rest of the config file.
Remove or comment out this line and try again.
When using more than one graphics device YOU MUST specify BUSID with each card, otherwise X does not know which goes to which and will not start.
Taken from Xf86Config man page:
This information can usually be found by running the X server with the -scanpci command line option.
PCI:1:0:0 refers to a agp card while PCI:0:1:0 refers to a pci card. - replace the 1 with correct values.
Everything else looks good and "should" work!