This is a hard post to reply to because of it's complexity. I mean there are so many aspects to the question you are asking. I think only a professional will be able to answer your question and be able to provide you the correct answer.

What I can say from my personal opinion is I think the type of abuse your mother has over you and your siblings is a controlling emotional abuse. And since I'm not sure of all the details with the sexual incidents I'm not able to say she's a sexual abuser, but I have a feeling she is. Especially since she was as a child.

I would definitely speak to a pro about this issue. It's very concerning and can eat you up whole if you continue to suppress it.

Those years that you don't remember well may be suppressed memories. You'll never know what actually happened unless you go see a pro.

I really wish you the best and I hope I said something you can benefit from. Please let me know if you need anything.

Cheer up okay, don't let her bring you down, that's another way she has control.....by hurting.