I agree on PD's role. He will be her guardian angel and will treat her in a brotherly-sister way rather than in a romantic way. I think he feels guilty for his wife's death and because AJ resembles his dead wife it was a way for him to atone for her death. AJ and Han Nee will be the bridge to help PD reconnect back with his son so that they don't miss out on the opportunity to be a family again.
YW imo would not be a great match either. He is idolizing AJ and having the "the one that got away" syndrome. So, I think it's best he find a real love.
Yes, it's cantonese. A