Michaela
As awful as it sounds, isnt your undivided attention currency? Those walks/drives started for us around the same age. I learned to do a lot of uh huh, with a targeted question now and again but I just let him ramble and then when home, announced it was play by yourself time or tv time. And mommy needs quiet time now. He thought this was very strange but in retrospect my protecting of my sanity actually also taught him to play by himself and not depend completely on others for his amusement. Now, four years later he plays by himself quite well, and is more respectful that conversations are two way streets but still will have to negotiate the I want you to play with me, but I don't want to do that, but why not, and then the myriad ways he attempts to get me to do it because he is SURE that I will want to do if he just keeps talking, he thinks it's fun so others should too even when it means doing it exactly his way in a manner which makes one feel like a chess piece. I am so much less amenable to this than my DH and apparently along with the lay down the law, I am also the one who has to teach him that other people have free will which means the right to not do it his way, and the right to not have to listen to him all the time. I might be a little vigorous in my teaching of this lesson sometimes, especially when I have a headache smile.

The intense focus all of the time can spoil him for other people because everything less is less enjoyable but intense focus for periods of time coupled with him doing what you or others ask is appropriate and developmental. I think all the time of anything is spoiling, not the intensity of the focus

I think safety always has to be paramount. I hated those leash/backpack things untill watched a friends kid walk right into the street,over and over again - any chance she was free would make a beeline for it, it was insane, she stopped doing it after probably a year, but if there wasn't a fence, she was too dangerous to be out of the stroller or unleashed. So it's legitimate to start demanding more than 20% compliance. But he's a smart kid, he will resist that change, until as they say it's futile to not. But as hard as it is teaching him to get out of his head when he needs to, or you need him to, is really important.

I think it makes everything so much harder when your kid is the square peg everywhere else, it makes you want to make one place for him where he can be himself and get that well filled up -but that can't be at the expense of safety, yours or his, or your sanity.

DeHe