Yeah I all ready thought you tried all of the above steps.
You're saying your a Apple fan boy and this is your first trip trough android wonderland

But you know much more then you want us to believe you do... (I think you' e got more knowleged about android/kodi comparing to the average user..)
Nevertheless it couldn't do harm asking if you did try hose few thing...
And about going back to 14.1 Im pretty shure rolling back firmware or Kodi version isn't possible because first of all you would need the firmware you want to role back to..
And only ones I know having it are the cood-e team..
Another possibility to role back firmware install would be through flashing a recovery backup.zip but you don't have one.
A recovery ,zip is a flashable backup.zip file normally made in a custom recovery program like TWRP or CWM recovery.
The backup file allows you to undo everything that was changed, installed or deleted by installing the firmware update.
So if you would flash the backup recovery zip your box or phone will be exactly the same as it was before youve updated firmware.
Only thing you can do for now is hoping coode team will fix the lagging in the UI so it will run smooth and your coode will feel snapie again...