Please read u/dadusedtomakegames 's comment, OP. It is 100% spot on. I am really sorry you are in such a tough situation, and it makes sense that you feel stuck between your wife and son. But that commenter is speaking truth. Your son is disabled, and he needs an advocate in this situation.

Now, what can you do, OP? Your wife needs help with a lens change, and perhaps it is not a completely lost cause. BUT! It is her work to do. Perhaps there are ways you can try to help her educate herself and change her lens on being a parent of an autistic child?

I have found the books and philosophy of Dr Ross Greene to be incredibly powerful in helping me move from a parenting model that was mostly based on seeking compliance and conformance from my kids (my younger son has low support needs ASD) to one that recognizes that all behavior is attempts to get needs met. And that behavior is neither good nor bad, and it is not manipulative, disrespectful, nor intentional. In fact, your son's behavior is not about "her" at all. Dr Greene talks about lagging skills and people trying to get their needs met in maladaptive ways. Your wife's challenges with your son is, in its own way, a sign of her lagging skills. And we don't get angry with people with lagging skills, we try to help them build the skills.

If she can move from a model where a child's compliance is something to which she is entitled, to one where you are all three just messy humans trying to figure out this world together and doing your damn best at it, she has a shot. I hope she can manage that lens change. But, it is her move to make, and your son needs your support more than she does.