So after 3 viewings...few more thoughts...
1. The two punches Arthur receives are both to the head and are both meaningful - the first punch trigger his psychotic aggression side (hence the ringing in his ears). The second punch, by Wayne, triggers a separate personality that allows him to truly embrace his illness and who he is.
2. The fridge scene - dunno why I didnt think on it before, but its clearly his safe place like when he was in the nuthouse. It has the same window in the front door as his room did in the flash black. Bright lights, 4 walls. Dunno it really symbolized...maybe nothing more than a safe place.
3. I'm starting to believe that Arthur is not the Joker we eventually see as Batmans nemesis. This movie is the origin story of Joker the idea, not the man. Arthur put things in motion...gave people the idea that someone like the Joker can exist. His need to be noticed resulted in the Wayne's death, Bruce being put on the Batman path, etc. But ultimately, hes not the Joker.