I've lived thru teenagers thoughtlessly using up my stuff, dodging responsibility, lying and being disrespectful.   You sound very patient, I commend you.  If you flash forward, you will probably see a young man being irritated because a roommate, spouse or child is using up his stuff, dodging responsibility, lying and being disresoectful.  Lol.    I laugh to myself when one of our grown kids makes a complaint like this.  Payback.

OK, from direct experiece living with people who do not clean up after themselves (DH and OSD) I had some pretty hard and fast boundaries FOR MYSELF set because anything I said was met with the excuse of "Cover is just too demanding and her standards are impossible to meet." Yeah, because sorry, I love dirty dishes piled in the sink, food literally on the floor and the counters and dirty dishes left in the dining room and living area. Putting things in the dishwasher by the end of the day is clearly "too demanding." And I'm only talking about kitchen stuff here which is the focus. 

I get you. If you are using the kitchen and there's multiple people in the house then if someone doesn't clean up then the next person has to usually move something to do what they need to do. I just explained this to DH for the 30th time last night, that I wasn't doing all his dishes but I needed to take care of some of them in order to do what I myself needed to do in the kitchen.  I think he may have actually heard me this time....but no bets.

So here's what I did when both DH and OSD lived in the same house (at least EOW). I asked, I discussed, I pleaded, I got angry, I did it myself. All to no avail. No. One. Gave. Two. Cr*ps. So I started just leaving them. But back then I was still cooking most meals. So then I had to clean at least some of them to cook.  So here's what I did.

* If I couldn't cook a meal because of the mess or not enough items were clean that I needed to use (pots/pans/knives/etc.) I simply didn't cook. And if asked, straight up said, "I cannot cook because the things I need are all dirty."   This includes counter space and things left on the stove.

* If I actually did NEED the space I would pile all the dirty dishes on one side of the sink or the counter and leave them.

* If, and they did, complain about any of the above, I would clean the items myself when alone, dry them and put them into a box set aside for donation. Because if no one else cared, then they must not need them. The more expensive pans and knives I kept in another space for my use only and I'd clean them and put them away when I was done with them.  I donated a lot of utensils, plates, bowls, glassware, etc. If we ran low DH had to replace them (thrift store trip).

* I did move to disposable items for about a month at one point. Things improved then a little. Because they haaaaated the "waste" of it.

* Nothing was ever better than making DH do the work. I stopped ranting and cajoling. I just left all stuff that wasn't mine there. I still do this with DH. I refuse to do a grown man's dishes (or YSD16s for that matter - she will take care of most of her things, but leaves "choice" items out for others to do for her) and he knows it.

For items being used you don't want used/eaten, you do need that hiding place. It's not enough to assume entitled persons will stay out of anything. And I personaly would not have drunk that coffee!  Nope. Are you sure it was just coffee?

OP, you MUST have a conversation with your SO about what his launch plan is for his lazy, angry, maladaptive kid. And you need to have a different conversation with yourself about limits and how long you're willing to put up with this crap.

Get some black rice or chocolate sprinkles and give yourself a "mice infestation problem ".   Choice spots in the house.  Include SS room.   Then lose your mind on everyone.   Go on strike until you win this battle.  Make it more comfortable to clean up than listen to you lose it.  

My SD17 has only one chore to do here too -wash her clothes- which equals to her only having to do 2 loads a month (one EOW she is here) but guess who was too busy to do it this past weekend? Yup! She laid around all day Sunday but didn't do it. She's here tomorrow night and just before she gets here I am saying to DH " Did you want SD to do her laundry tonight since she didn't this past weekend? If she doesn't then she will try to cram it all with her other things next weekend and overload the washing machine" I hope he does tell her otherwise it's allowing her to disregard his wishes because he was the one to tell her to keep on her laundry and not leave the towels in the hamper for 2 weeks. 
She is truly "Miss Bare Minimum" about everything!!!!

I have the same issue with SD16.  She does not do a thing and is not fond of her 1 chore she has to do per day when here (her and the my girls all rotate between dish washer duty, vacuuming and bringing trash out).  She will often leave her dirty dishes or any trash she has accumulated exactly where she was. I've gotten on DH to get on her to do her whopping 1 chore but he is inconsistent...she still hasn't cleaned her room or done her laundry since the beginning of February...my pet peeve is that she will go to eat or drink something and leave 90% out to go bad or put back in the fridge-then not finish it. I can't say much because she has an eating issue and the goal is just having her eat in general.

I've already had the conversation with DH that once she graduates, she is not staying here (she comes on w/e's..when she can't get out of it).  She can live with birth mom until she's 40 (it's not just her but all the kids)...the stipulation for all the kids is if you go to college- u can stay, or if you don't want to go to college (at all/yet) that's ok, you can stay 1yr while working*. That's your year to figure out your plans. SD had one part time job at Burger King and quit because they went too fast and she wants a job that is slower paced..needless to say she is jobless.  

good luck lady!

He had the nerve at 17.5 to tell off his dad it was my job to clean up his dirty dishes since i was a stay at home housewife with a newborn when he was freeloading and mooching off daddy.

biatch, your own mum didn't lift a finger to do housework and you want to demote me into your little bitch?? Nope not happening.

hubby told off his kid it was never and jot my job to clean up after lazy bums. 
 

anytime we had water pipes being repaired and water came out slowly but was coming out enough that you could clean dishes, ss saw that as an excuse to not clean dirty dishes. His dad was on him instantly 

whenever i came downstairs to a sink full of dirty dishes which attracted ants, i took a picture of the mess or trash dumped on floot next to bin of all his takeaway and sent a message to hubby at work that said "your son's mess, address this now!!" To which hubby immediately contacted ss and ordered him to get off his lazy arse and clean his mess pronto

now because of all this, ss lies to his dad in private trying to paint me as a bad neglectful mum full of lies and hubby everytime tells ss "i know that didn't happen because i know what goes on during the day with my wife and our 2 young kids"

in front of his father, and call him on the milk, cherios, and coffee.

Lather... rinse.... repeat on each and every idiot move he makes. Increase the pressure, he will leave.

Make that the goal.

Good luck.