Responses

Not really, but it shows some sort of respectful distance between them.
Family members are most likely to call each other like by their nickname or as son, wife, dad, brother, and so on. Compare it to the way LiHuan talks to his parents: they call him "son" or "HuanHuan"; he calls them as "mom, dad, you" (neutral).
When YuYang was speaking to his dad he also used 您 nín, a respectful manner to say "you". When he changed his tone, he refered to him and the others as 你们 nîmen, a more usual and neutral way os saying "you (plural)".
Chapter 51: https://mangadex.org/chapter/447173
Tension built up to the ceiling, this time......