This director is now on my top 3 for cdramas. Aside from the traditional creative and artistic skills typical of a top notched director, what I appreciate in Zeng Qing Jie is his ability to make his viewers not only root for the leads and good guys, but also feel for the villains. We're talking about the Sui brothers and PM Wei. I didn't read the novel, but from what's been presented so far up to 17, I still don't know how bad PM Wei is. Maybe I should thank the casting manager instead because all the main characters are so well cast.
last ep he did not want to tie her up with his mess (he said to his friend) but this ep he asked her to come with…
He's in love with her, but he's on a life-and-death mission. He doesn't want to turn her into a young widow should he be dead. It would be very difficult for her to find another husband/man as a widow in that society. So, in essence, it would be selfish of him to put her in that situation should he starts a real relationship with her yet ends up dead in a few months. At the same time, the idea of another man kissing her and talking about her fair skin is enough to make him angry. He's conflicted.
Adding to your summary, GongSun family is banned from court practice, so his ancestors probably committed a crime and got punished.
It was said that when East Palace was burned down, one person escaped. I believe that escaped person was Qi Min, making him Yin's royalty.