Your mother cannot help you make sense of this situation. You really need to stop trying to get her to help you figure this out or agree with you that it’s fucked up. She is one of your abusers, IMO. Enabling abuse is abuse. Being so damaged you can’t see a man sexualizing his own children maybe isn’t her directly abusing you, but she is complacent. She is an adult who was tasked to protect you and she hasn’t.
You’ve said in other posts that you are in therapy. I noticed you didn’t mention that. You really should try to get into therapy.