He's not the first malignant narcissist who tries to cover his personality disorder(s) by claiming to be autistic. It's insulting to people who really are autistic.
His insults--relentlessly accusing you of not being "normal" because you're neuroduverse--that's gaslighting. It reminds me of a narcissistic sociopath from my past.
I'm glad you divorced him. It's empowering to stop having narcissists and sociopaths in your life, but it sounds like you need his financial help in supporting your kid. At least you can limit your contact with him.