As far as i know, there is not Global variable for blueprints. Also accessing the LevelBlueprint in other Classes is only possible with EventDispatchers or BlueprintInterfaces.
But what you could do is using the GameInstance Class. Just make a new Blueprint deriving from Game Instance. Create your variables inside. You can get it everywhere with the node “GetGameInstance” and cast it to your specific custom class. This should be global and also live over levelchanges.
http://puu.sh/dkHcC/6cc185e22e.jpg
Does this solve your problem? If not, feel free to ask me.