Indications are you're running Xvesa, otherwise first line of .xsession shoud read similar to: /usr/local/bin/Xorg -nolisten tcp &
Your onboot.lst is missing Xprogs.tcz (essential). Here's the most basic onboot.lst that i believe results in a working Xorg system. Subsitute for your preferred window manager and video driver.
xf86-video-intel.tcz
Xorg-7.7.tcz
Xprogs.tcz
fluxbox.tcz
aterm.tcz
Your xorg.conf file is obvioulsy not being utiized as your xorg.conf and xrandr screen resolutions don't match. Try a very basic, simple xorg.conf file. Reboot system and check xorg.conf, xrandr and .xsession for resolution and persistent reboots. If your system isn't running in persistent mode then the changes won't take effect at reboot. Here's a good, basic xorg.conf file, change to your preferred driver, etc.
Section "Monitor"
Identifier "Monitor0"
HorizSync 28.0 - 96.0
VertRefresh 50.0 - 75.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Card0"
Driver "intel"
BusID "PCI:0:1:0"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Card0"
Monitor "Monitor0"
DefaultDepth 16
SubSection "Display"
Depth 16
Modes "1152x864"
EndSubSection
EndSection
Have you tried nouveau driver?
Since you have old hardware, may want to try TC 4 which may have more appropriate older kernel, Xorg and video driver.