I also think if I can manage to run a home and live independently then he can as he's much brighter than me, he doesn't like house rules or authority and struggles with it so I can't imagine he would want to live at home with any restrictions forever. I know I couldn't.
He is not like you. He may be "brighter" than you in some ways but he is still like a child in others. He is still dependent on home, and on you, and he is deeply in denial about it. And as long as you keep giving way to him why would he ever want to leave? It is you and your DH who are being restricted, not DS.
You also need to recognise that for example what he says about parenting standards is nonsense, it is just him trying to make sense of his own anxiety and control you with logic.
You and DH need to start making house rules that suit you and not just DS. Times when he either has to be out (regardless of whether he wants to go out or not) or in his room, and he does not come downstairs. He needs jobs that he needs to do around the house. He needs to respect your privacy and your husband's. A lot of ordinary housemates would not tolerate his behaviour in his home which is also their home. So if he is ever to learn to cope in his own home with a partner or friends (other than living alone) you and your husband need to start teaching him those kinds of boundaries and respect for others, by setting them and insisting on them.
If he found a partner he could easily become controlling and a bully to her too. When his partner did something he didn't like he would tell her - as he told you - that he had High Standards For Wives and maybe (because he is clever about other things) she would believe him and try to live up to his standards (like you do as a mother). Instead of realising how incapable he is.
You must set some authority and rules, whether he likes it or not. Otherwise he will become increasingly dominating and you will have less and less of a life.
I can believe that you all have autism but it affects each of you in different ways.