Questions (cleavage, incest, ...)

1. Why all the cleavage? (Those weren't historically correct costumes, right ...? It's hard to find historic relevant material if you search for "chinese cleavage". ;) It seems "The Empress of China" also contains such overexaggerated cleavage. But why it earns so much more criticism is beyond me.)
2. Did the middle son (the empress's first real son!) and the empress also have an affair? (I thought they almost kissed and the looks when they were reunited. The affair with the king's first son began three years ago when the middle son was sent away. Maybe that was also part of the reason for sending him "to the front". Plus the youngest son seemed jealous.)
3. Why make the Imperial Doctor governor only to kill the whole court? I mean the emperor could have killed him before at any time I guess.
4. What's with the romantic, joyous music at the end when the poison/acid sprays on the family table? For anybody understanding Chinese: Do the lyrics fit the situation?