TechNet hasn't gotten back yet but I was looking through it last night and I noticed this error repeating a few times
2014-07-18 13:43:40, Info CBS Failed to internally open package. [HRESULT = 0x800f0805- CBS_E_INVALID_PACKAGE]
It means The package is not valid. Only ones from Microsoft can be installed. But it doesn't say what package it is referring to
There is another log - c:\WindowsUpdate.log - Search in that log for the word FATEL it should like this 2006-08-28 09:17:03:927 1100 e00 Handler FATAL: CBS called Error with 0x800f081e if you have any post it here or you can just post the whole log in onedrive.
c:\WindowsUpdate.log
I would look at windows update to see if any updates are missing. You may want to make a systems image or you system using File History > Create System image
Then Make sure you have recovery media. Once you have all your data and a copy of your system try uninstalling the major updates to windows and the reinstall it. Pretty sure it is kb2919355
If you have windows 8.1 recovery media I would try a refresh your pc http://windows.microsoft.com/en-US/windows-8/restore-refresh-reset-pc