It's normal for a CBS.log to be big. I've seen one that was 4GB of size. Once it gets to a certain size, Windows will automatically archive it and a new one will be created. Well this being said, SFC returned a clean CBS.log. Now can you try to install the updates again? If they fail, upload the following files for me to review.
C:\Windows\WindowsUpdate.log
C:\Windows\Logs\CBS\CBS.log