I don't know where to begin with this! Sorry, but your DS sounds really quite unpleasant.
OP... you need to stop being so servile with him. Ditto on your DH. You both need to grow a bit of backbone, stop treating on eggshells, stop running around treating him like The Last Emporor. He isn't. He is a grown adult who needs to treat his parents with the respect they undoubtedly deserve, especially if he wants to carry on living at home.
Re the job applications. I went through this with my DCs after Uni. I knew it could take a long time, and one of them it took a lot of applications, but I told her she had to treat getting a job, like a job in itself, i.e. start at 9am and work away at it ALL DAY. She did on the whole and it paid off.
My DCs have had all manner of punishments in their time, they are now independent adults and we have a grown up relationship based on respect. Your DS saying that he speaks and you listen... well, I have steam coming out my ears on that one and he ain't my son! Tell him a conversation is two people talking, two people contributing to it, give and take, listening, hearing, answering, ... not him expecting you to nod along to whatever he says! If you don't hear what he says nd he won't repeat it, well... I would go apeshit to be honest..
OP he is treating you with absolute disdain. He is 23 FFS. He should be helping you with computer problems, telling you plots of films, laughing with you about family stuff, cooking you a meal for a treat, generally being part of the family. It's what my DSS does and my DDs too. Your DS is acting like a sulky 13 year old.
I have a friend who has treated her now grown up sons like this, she never even dared ask them a question when they were teens, because she wanted everything to be perfect so didn't like to! (she couldn't even say "how was school" for fear of upsetting them). Now, they are OK with her if they get their own way about absolutely everything. If she dares to question anything, however small, one of them in particular will freeze her out for weeks or months. He lives away now and will literally cut contact over something minor until she grovels. The other treats her like some sort of servant and thinks women should keep quiet and be stood at the sink or cooking. What delightful boys she's raised. Not.
I wouldn't suggest writing out a list of rules. To go from nothing to that is too confronational. However, you should change your mindset and your responses to him starting now!