OP I get your exhaustion and frustration. Which make everything else harder to deal with. It is a really tough situation for you. And for your son.
Autism and/or ADHD and/or absent father and /or knowing on some level that his mum resents him, can all contribute to very difficult behaviour that a 9 year old genuinely can't help.
Underneath it all he is probably a very frightened, confused little boy who feels rejected/ abandoned by his father (whether he remembers him or not) and insecure in terms of his bond with hus mum. That's tough already, add in autism and or adhd and life gets even more difficult for him.
.. so I'd really encourage you to leave some space for reasons other than "I know majority of it is just him being a sh**".
It's not necessarily a problem that you think that sometimes, you're human and sometimes you might be right, but it's not fair or accurate to assume that generally the problem is inherent nastiness in him.
Probably all the things listed at the start of this post are part of what's going on to some extent. That doesn't make the behaviour easy to deal with at all.
But it does mean that you both can get some support and understanding in this very tough perfect storm.
If you tell your GP/ his school you are struggling so much you're considering giving him up, they should be able to get things moving to helping both of you with therapy and support.
All the best with this very difficult situation.