This is an origin story. so 80% Arthur 20% Joker. Technically he becomes Joker before the hair dye and make up and all that but you'll understand what I mean after you watch it.
Yes it was pretty good, and nobody has shot up any theaters for this one so you're safe. They'll kick you out if you come dressed up as joker though. (Not that you would)
Well I think you should watch just if you want to know the story of the joker but it doesn't have many actions and explosions there