@dragynfaerie
My 2 cents:
The poster showed the head of LG with a head cover, similar to the cap that the savior wore. Also, one thing he remembered was that the savior was tall. The poster emphasized his height.
Regarding Yoyo boy, I have changed my theories about him several times :) From guardian of balance to some other deity. My current theory is that he is the spirit of Manpasikjeok since he said he wants to be whole.
Perhaps Lady Noh was a mistress or a good friend of LG's grandpa or Prince Buyeong or another member of the royal family, that was why she became head court lady. Or maybe she was just good at her job. I agree with your assessment that the point there was to show people have been crossing worlds even before.
I think LG is trying to get to the point in time when the Manpasikjeok was still whole, in which case Lee Lim would not have crossed worlds and Shin-jae would not have gone to Korea, among other changes.