lack of empathy drives me to my wits end

I'm a non-ADHD partner and my boyfriend was diagnosed as a young child with a severe case of ADHD. He was on Ritalin and Adderall as a child, which helped tremendously when he was young, but he went off medication as a teenager and has basically asserted that he no longer has it. 

We've been dating for almost three years and in my opinion, he very much has ADHD symptoms. The most notable manifestation is that he routinely cuts people off, seconds or even milliseconds after they start talking. We have very much fallen into the parent-child paradigm, where i nag him about things and i feel ignored when he cuts me off sarcastically. He also loses things all the time and is incredibly disorganized. In the past few years, he has lost 2 expensive fleece jackets from his parents, his backpack with all of his cycling gear in it, his $200 headphones on the plane, his phone, two baseball caps that he treasured, one expensive sleeping bag, and two expensive sleeping pads for camping. Before we started dating, his room was covered entirely in old beer cans and one time he drank from the wrong one, and took in a whole mouthful of mold.

The biggest problem for me is his general lack of empathy and concern for my feelings. I come from a culture where people are trained to notice other people's feeling or at least learn a pattern of behavior that is generally respectful and mindful of others' needs. Partly because of my background, I think i am particularly sensitive to his lack of empathy. However, I also think that it makes me less willing to be firm about the things that bother me, repressing hurt feelings until I explode in anger.

He is also very sarcastic. Whenever something makes him feel judged or criticized, he immediately starts making sarcastic jabs at me. Even when I am not being critical, he uses sarcasm against me. For example, rather than asking me if I want dinner, he says "I guess you don't want any dinner," and then storms off and starts cooking. Or if I take a long time to think about where to go for lunch, he will scoff and say "I guess YOU'RE not going to make decisions so I'LL have to."

We've been going to couples therapy and we've learned a lot about his insecurities. What gets me the most, is that not only is he incredibly rude and sarcastic but that this also stems from his insecurities. So he can dish it out but he can't take it. These kinds of interactions makes me mad and resentful and unable to be empathetic to him, and I find myself treating him the same way he's been treating me. And he knows that's the case, so he gets angry and say s "why can't you just be nice to me and eventually i'll learn from your example?,"which i find to be bullshit since I've already tried doing that for a year, but to no avail.

Today I confronted him about a bowl of mine that he broke (also, he doesn't own or buy anything in the house; all the furniture, household supplies, utensils, etc were contributed by me), to which he said "That's not your bowl," I replied "yes it is, it was given to me by a friend." Then he said "Why would you expect me to tell you about it?" and then "It's not like I meant to break it" and then "I'm sorry?" as a question as if he were filling out a multiple choice exam. 

I'm totally at my wits end and I am really wondering whether it's best to get out. His parents are actually in the process of getting divorced, because his mom is the same way. Thanks for letting me rant.