marklovescoffee; Welp:

1) Release 14.10 will reach End-O-Life this July, no point in wasting resources and effort there.
2) Repair the current install - vivid : doable, just takes time and effort to isolate and repair. Well worth the effort for aiding us in progressing up on that learning curve.
3) A fresh clean install is always a good thing when the situation gets out of hand and/or becomes the expedient thing. If one keeps back ups of their personal data it is but a matter of 20 minutes or so and all questions are answered.

I am always for advancing on that learning curve. In this situation my considered opinion is to purge the no-longer-needed xorg-edgers PPA and it's driver, purge the graphics driver and install the driver the system recommends from the ubuntu software repository.
Once that is done, clean up the system and make sure the package manager is stable and in a happy state.

If we are to install a driver from the repo ( a conflict in drivers ??), I need confirmation as to the display manager that kubuntu uses :
LightDM is the default display manager for Ubuntu, Edubuntu, Xubuntu and Mythbuntu since 11.10 release, for Lubuntu since 12.04 release, and for Kubuntu beginning with 12.10.
Code:
dpkg -l lightdm
still valid in 15.04 ?

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It's your time and your effort and your system;
your decision as to what to do
we are here to help