Oh you poor pet OP, that sounds awful and lonely.
You sound very much like feel you are excluded by your Mum.
Of course he sounds awful. The teachers saw through him no doubt.
You have had some very, very hard experiences when you are so young.
Unfortunately, we cannot change other people, much as we would love to, and try to.
Your mother is wrong, has chosen very wrongly, but there is not a lot you can do about that.
However, what you can do, is not be defined by it all.
You can choose a different, and better life for yourself.
MN is a wealth of good advice, and great suggestions, on great books to read.
Help yourself, and you can have a better life.
You sound like a great, clever, self aware girl, someone who is very bright and intuitive.
You can do this👍