Is it time to go?

We've been married for 30+ yrs. Husband was diagnosed when he was 50, but we struggled long before that. He takes meds, goes to therapy and says he spends "so much time" working on his ADHD. We've gone to couples therapy and taken Melissa's class twice. I've gone to therapy multiple times as well. Despite all this, to me it feels like his ADHD is untreated. I've tried to help him with docs and treatment but he needs to help himself.  He suffers from severe RSD, which I think is the root of so much of what we struggle with. He takes guanficine, but it doesn't seem to help. The ever so smallest thing sets him off into an irritability spiral and he's snarky and mean. I manage all things that require any attention to detail, I coordinate 99% of the details of our lives....... it seems like he only hears 25% of what we talk about. I never know if he's paid attention to stuff so I can't count on him for many things. When I ask a question about something we've talked about multiple times and he doesn't remember talking about it he gets all irritable and lashes out at me. Sometimes he says he's sorry for lashing out, but there's usually an excuse ..... "oh I didn't sleep, my phone isn't working". I'm exhausted, angry, sad, lonely and frustrated. I've told him multiple times that I'm at the end of my rope and something has to change. He makes some changes for a week or so then we're back to the same place....... over and over and over. I'm not the happy, fun creative person I used to be. So often he sucks all the joy from me. After his little meltdowns he can snap out of it and make jokes, but I'm spent and can't "snap out of it". So I stay angry, frustrated and cold towards him because I'm just so tired of being treated like that. We retired a few years ago and I thought things might improve since we would both be less stressed, but that hasn't been the case. He gets so hyper focused on various things that he's oblivious to everything else. When I mention the hyper focus  he says "oh I guess I just can't do x - I'll just quit doing that". 
For a long time I kept thinking he could find something..... therapy, new med, new tool........that  would help us, but I now realize that's not going to happen and at almost 70 he's not going to change. I'm struggling with making the break, financially it will be hard. I often think "who will take care of me when I'm 80" or "I don't want to be alone" ...... but then I realize how alone I feel now and wonder if I'd be better off calling it quits?????  I read all the stories here and I'm not optimistic that we can make it work