You should create a game instance, and store thoses variables in, it will keep them all the playtime and then it s free to you to save them in a savegame.
I don’t know your knowledges so I keep going:
From the BP you need the variable, at event begin to play cast to you game instance and promote it to a variable, then you can get any variable from the game instance and once again you won’t have any reset probleme while changing character or even level.
For the HUD, displaying it in gamemode is how I would’ve done too.
If you want to keep anything while changing character, don’t store it inside it.