There is no need to uninstall FTM2012, just unlink the FTM2012 file from your ancestry file. If you haven't already, put the text string "2012" somewhere in the name of the FTM2012 file and its associated Media folder, so that you will remember as time goes by that this was an FTM2012 file. This will also reduce the possibility that your ancestry file will try to link with this file.
Then install FTM2014, but DON'T Open your old FTM2012 file with FTM2014.
Once you have registered FTM2014, or FTM otherwise recognizes the ancestry file as yours, go to the Plan workspace and choose to have the ancestry file linked to your computer from scratch. FTM should create a new FTM2014 file and you should be set to move forward.
Be mindful that these steps are if you want to continue syncing in spite of its many problems. If you don't want to sync, and I suggest you don't sync, you can still backup your ancestry file to your computer the old-fashioned way - a simple one-time "snapshot" backup from the Plan Workspace into an FTM file.