I didn’t mean to send the message that he shouldn’t have to listen. Yes, he certainly should be expected to do something that’s asked of him. The trick I’ve found with myself (I have Inattentive ADD) is that if it’s something small like putting dishes away or starting the laundry, as soon as I think of it I have to do it RIGHT THAT SECOND. Otherwise it won’t happen. Don’t go to him while he’s playing a game or doing homework or watching TV and say “remember, it’s your turn to put the dishes away tonight.” That will inevitably lead to YOU (or mom) putting the dishes away, and he will only remember once someone else puts them away and then feel guilty about it (“see? I always screw up and forget to do things. Next time I won’t bother. They already expect I won’t do it or I’ll forget, so why should I try? I don’t need to prove that I will screw it up again”). Instead, find a point where you can say “please put the dishes away” and it is something he can do RIGHT NOW and then provide that positive reinforcement as soon as he’s done. Yes, it means that you are the one identifying when to point out that it’s a good time to do that, but it also avoids a scenario where you say it five times before there’s an opportunity for him to actually do it at the same instant you make the request. The nagging is draining on you and degrading to him, as it feeds his internal narrative of “I can’t remember anything.” If you can ask him to do it at a moment when he can do it RIGHT THEN, you’ve astronomically increased his chances at succeeding in the task and getting that pat on the back for showing that he can be helpful (and by extension, showing himself that he really is capable of getting things done).
One last thing, as you probably have seen already in your research: he needs constant reminders that it’s OK to forgive himself. He’s still a capable person even though he sometimes makes mistakes; that’s a hard thing for most teenagers to accept, and an ADD teen is starting on the back foot in that department.
Keep reading, researching and applying. He’s got a great start with a mom who is sensitive to his neuro-processing differences and a loving stepdad who is trying to learn how to best support his development into a successful adult. I wish you all the best.