Why would you feel bad that your husband has to take care of his own kid?

You make two different dinners? Oh, heck no. 

He sounds like a spoiled brat. Stop allowing him to treat you poorly. 

The point of disengagement is to give you peace of mind.

You can still make dinner, but you make ONE dinner. SS can eat it, make himself something else, or have DH cook for him. You can do laundry, but leave it up to SS to put it where you want it so you'll wash it and then put the basket of clean stuff back in his room to take care of (though I personally think ALL teens should know how to do laundry start to finish). You can keep clean the common areas and your own room, but leave SS's room and bathroom up to him to clean to YOUR standards (this is what I do with cleaning for the SSs; they know my standard, and DH makes sure that it gets cleaned to that standard whether he or the boys do it).

I'm similar to you that I like doing things for my family, but I have had to take a step back and let DH handle some things. Though, my SSs are appreciative of what I do. I'd be far less inclined to do things for them if they acted ungrateful.

OP, it's fine to care for people, but also keep in mind both you and youe husband are trying to raise functioning adults - not raise children.

Both your ss AND daughter should be helping with laundry, cleaning, cooking. If you don't teach them, how will they know what to do when it is time to start their own life? 

Kids eat what is prepared or they go hungry.  Keep it simple.

to tell your SS exactly why you will no longer do things for him. He is old enough to understand the concept that if he is totally unappreciative, that you will not lift a finger for him. Why would you do his laundry? I would not touch my own kids' laundry - has not been my job since they were toddlers! Too much work. The only positive for you is, the more competent he is, the better chance of successful launch and not getting stuck with him when he's 18+. I would tell him - he may appear to ignore you, but it will be in his head until he is mature enough to fully grasp it. I have occasionally had discussions with my own kids about understanding they need to be appreciate of what I/DH (their stepdad) does, and they get it. 

which my kids and hubby eat fine. Ss is into unhealthy food and when i’ve cooked dinner makes drama like he needs chilli sauce and has to drive to convenience store to get some so i do not cook for ss. I cook and me and kids eat, hubby eats and its upto hubby to make ss21.5 eat but i do not call him because he’s a rude prick.

try having hubby from work tell me to knock ss door saying dinner is ready and ss mumbling jibberish i don’t understand and eventually i go eff this and tell hubby he can effin get it himself, i’m not his little bitch maid!!!

I am a nurturing person. I like to take care of my family. I like to cook. I like to do laundry. I like to clean.

Me too - but only if it's appreciated, then I run into a brick wall and don't continue to help.

However, I am now finding the need to disengage from my SS. He's not a terrible kid. But he takes me for granted. He takes care foe granted. He pretty much only talks to me when he needs something. I'm tired of it.

Why?  I see that he takes you for granted, but does your husband correct his attitude?  Do you grant his every request, or does your husband?  I suspect he's got some attitude about it too and itsn't exactly polite and your DH ignores it. 

Do I stop making his dinner? (Unfortunately we have a situation where my BD and SS usually eat different things and until recently (they are both young teens), I've accommodated this. Do I continue to make his dinner?

You stop catering to individuals at dinner time.  Cook one thing for everyone.  You can make it something everyone will like.  For instance, I'll sometimes make turkey meatballs and pasta and hold the red sauce or pesto aside for DH and I since YSD refustes to eat sauce.  No biggie.  However, I will not make an entire meal JUST for a skid.  OSD used to refuse to eat ANYTHING on the table.  Fine then, go make yourself something else.  DH used to step in and make something extra but I refused to delay my meal because of OSD.  And he got really tired of helping every night. 

What worked for me was unapologetically letting DH know that I was not to be the main meal cooker/provider when SDs were with us - HE had to do most of the meals.  If I chose (I chose) to cook, then I would make only one thing.  No special orders.  If DH wanted to make a second meal, that was on him.  And if OSD wanted to make something else, that was on her and we wouldn't delay our family meal.  OSD hated, hated not being in control of this but I could have cared less.

But then my husband has to do it. And I feel badly about that. I want to take care of him. But not SS. 

Let him take care of it.  It's HIS kid.  You didn't raise him to not help or not join in a family meal.  If your DH doesn't back you up 100% of the time, you will never, ever change anything.  If you have no authority you cannot have any responsibility.  And another thing - DH is a grown man.  He shouldn't need "taking care of."  I've stopped helping DH with things along the way too.  I'm a grown woman and don't have to take on another adult's mess.  He is capable, so he can do it.  THAT is what SS should be learning. Be carefull SS isn't picking up on this, OSD did with DH (hey, BM is helping DH with his dishes, she can just do mine too). 

And about laundry - I stopped helping with all SDs laundry when we bought a house together.  Brand new washer/dryer.  I taught both SDs how to use them, about 2 run-throughs, and posted instructions on the cabinets.  YSD, then 10, now 14, since then did all her own laundry - including bedding and towels.  OSD, I think NOT ONCE did it on her own, from age 11 to 13.  DH always had to step in and "Help" - i.e. do it for her beacuse...learned helplessness.  "I don't know howwwwwww...." even though she could perfectly well do it.  So no, don't feel bad about it.

...DH is in charge. That doesn't mean that he always takes responsibility, but I don't cook for SKids, I don't clean up for them. Sometimes, I will buy them things they need, but I've even cut back on that significantly because usually people complain about what I buy or claim that I don't buy them anything. Also, I refuse to be a mind reader and despite my inquiries, I am never told when things don't fit, when things run out, etc. 

Getting absolutely zero appreciation from stepkids, is a huge demotivator for me, leading me to disengage to reduce my level of resentment. DH might be annoyed by it, but they are his kids, and I am under no obligation to provide for them.