@Reacon unfortunately, what you're doing will not work with the retail version. Steam uses a third party to update its games. Once the update has been completed, Thats it. it will NOT re update after you've replaced the game files with your backed up game files.
I unfortunately have the retail version and i do not know of a way to bypass the social club launcher. I dont want to really try either as i might update my backup lol. i could try disconnecting my ethernet cable, but im just being patient for now.
For all of you that have the steam version, you can still play with mods if you have a back up.