In the OT, zombie's book pretty neatly gets into why "I am your father" and "you are my sister" happened, which was to simplify and compact the backstory into something they could wrap up.

I disagree that Lando owning the Falcon before Han is problematic. It quickly defined their relationship. It was their connection.

In the PT I think all the Universe shrinking was to get a cheap cheer in the theater, "I will miss you too Chewbaca." In absense of a moving storyline, the movie could present moments like R2 meeting CPO and make the crowd happy.