Ok. I will await your note. from everything I have read, you tried pretty much everything I saw. In the meantime, I uninstalled the .Net4.5 and tried reinstalling 3.5. ( from the kb, not windows update) It looks like it is installing and then uninstalls. Windows update has 2 important updates waiting---- 4.5 and 3.5.
I will be interested to know what the sfc log shows--- you read these more easily than I do.