How to engage in conversation

I've been married for almost 25 years. My husband has never been officially diagnosed. During my first years of marriage, I believed our communication problems were due  to the classic tale of Men are from Mars and Women are from Venus. I tried all the different approaches that this sort of literature suggested. None really seemed to work.  A few years ago, a good friend of mine and child education; suggested that my husband may have ADD. As I began researching and taking workshops (one of my daughters has it) I've come to the realization that my husband also suffers from this. I've talked to my husband about it, and he's in denial. He doesn't accept it, therefore is not pursuing any help; because "that's the way he is".

I can deal with the forgetfulness, lack of help around the house, hiperfocusing, not being able to watch movies together; I've learned and am used to doing this on my own. What I can not get used to is not being listened to. Even my youngest daughter, who is just 6, always yells at him during their playtime "Daaad, you're not listening to me!".

I've tried speaking in "point form". I've tried speaking on one sentence at the time. I've tried pausing when I see he's mentally gone. I've tried the Q&A method. I've tried writing my thoughts (he has a terrible time reading too). 

It's normal for a spouse to want to talk about dreams, feelings, plans, ideas, etc. You want to share with your partner and make him part of you. But he's not there when I talk to him about deep meaningful matters. I can talk about the weather, dinner, kids' school matters, random daily stuff. Since this is not really meaningful, and "complicated", he's able to pay some attention. Usually these exchanges are short, and we can jump from one topic to another. But meaningful things... "couple" things, as soon as I begin talking; he's there for a few seconds and then he's mentally gone. Sometimes he comes back but he's missed so much speech, that he's lost as to what I'm talking about. If we're in bed, and I talk to him, he falls asleep while I'm talking, so I avoid this at all costs.

During a conversation, to be recapping all the time, it's tiresome and frustrating; because then the conversation keeps on getting longer and longer; and I can see how tired and uninterested he is by then. I feel like to his ears I'm the teacher from the Peanuts cartoon. Or like he just cancels me out and focuses on whatever is going on inside his brain. He's physically there, but not mentally; he's lack of attentiveness is so bad, that he can't realize when I'm still talking and just leaves to do whatever his brain told him to do, while I'm still talking!

So, any recommendations as to how I can help him engage in an intimate conversation? How can I just talk to him? I asked him once this question: Please, help me communicate with you, what can I do? His response was "I don't know", "just accept it, that's how I am".

Should I talk in "episodes"? I'm afraid that by the time the next episode comes by, he'd forgotten what the previous episode was about.

Should I just keep my thougths to myself? No meaningful conversations? I guess then our senior years, when there's nothing for him to do, we'll be very bored; since we can't be conversation partners. How sad.

What have you tried that seems to work?