DS1 didn't sound dissimilar to your little one.
I read all the stuff, and I'd done all the signing, all the outings, all the this, that and the other, but none of it worked for him.
He was night feeding at 18 months, he was still often needing a midnight snack at 3 - he just got hungry. We co-slept and then he was in the same room as us, in a toddler bed right next to me because he couldn't handle being alone, and I needed sleep. He couldn't feed himself, he didn't utter a word until he was 2, he was very self-contained - never did art, didn't remember anyone's names (still doesn't), just kinda pottered through life, accepting whatever I did for him.
He's 9 now, never shuts up (literally), at 3.5 some switch flipped and he just started sleeping through 7:30 till 6 (never lies in). He's dyspraxic - but that's just something to work around, and such a lovely kid, so easy, in contrast to the first 2-3 years (and his little brother, who's a more standard issue child).
My one thing is that we've never limited screen time - I read all the stuff, and decided that there's a world of difference between a child, slumped watching TV, and a child wandering around, standing on their head on the sofa, choosing which youtube videos to watch next. (plus we moved a lot, so they never had many other toys).
Your mileage may vary, but my unrestricted screen time kids are absolutely great. They have fantastic vocabularies, and a breadth of interests - DS1 learned his ABCs from youtube (I can still sing the songs), and recently got a prize for being able to name all the 2d shapes up to 20 sides - again from a youtube song. They use it to look up things they're interested in, still have playdates, do sports, cook, do crafts etc. They're able to put down their devices for meals etc. because they're not ever worried that they are wasting precious ipad minutes.