So many questions lol Bai Jue didn't forget Qing Mu memories, he is lying because he wants ShangGu to forget him and Qing Mu, Qing Mu is, after all, part of Bai Jue. Aqi knows Qing Mu is his father but also knows Qing Mu is now Bai Jue, he even asks Bai Jue to give his father back, is so sad. I don't remember cleary if he knows about ShangGu, I think he knows but also knows she forgot her memories and FengRan and TianQi tell him to only call her aunt.
Bai Jue marries JingZhao to keep ShangGu away so she can't discover his plan he wants her to hate him. ShangGu falls for his plan, when she starts suspecting him she recovers her memory as Houchi and pierces Bai Jue's body with her sword and condemns him to stay out of God's Realm forever. Thats what he wanted so he could sacrifice without her knowing. When she discovers everything is too late and Bai Jue is already dead. So she says she will wait for him forever.