EtreCheck and OS El Capitan/Mac Pro 8-core (early 2008)

Start with removing the kernel extensions

Kernel Extensions:
  /System/Library/Extensions
    gafwload.kext (1.0.1)
    gwauusb.kext (1.0)
    gwawusb.kext (1.0)

I'm not sure what they are, but they will not be loaded during Safe mode, and kernel extensions are often the cause for system failures.

Remove the two 3rd party anti-virus packages. AVG and Trusteer

Memory cleaners are not a good idea

Memory Clean 2.app

"Major Issues:
  Anything that appears on this list needs immediate attention. 
  More than one antivirus app - This machine has multiple antivirus apps installed.
  Obsolete hardware - This machine may be considered obsolete."

AVG and Trusteer are not very trustworthy.  Not to mention while enabled they can block 
operating system installs.
Also noted CS2 is probably not El Capitan compatible.  Check http://www.roaringapps.com/
Also check for QuarkXpress.

All startup items may need to be upgraded for El Capitan and all Launchdaemons before booting 
without safe mode can be accomplished.