PUPPY!!!!!!!

That's exactly the situation I want to avoid; I want him socialized around other people and other dogs, and I want him to be comfortable with others watching him when need be.

I'm alone but definitely not (probably everyone says this) a loner. A bit more so since I moved out of the city in late 2019, but I'm always out and about. That's the adjustment: not being able to just head out. Pre-pandemic, I'd go see one-three movies a week. I constantly just head out to browse book or record or thrift stores. Going out to have coffee and read. Going back to the city to see friends (a two-hour drive). All of it breaks up the day, being retired. Right now, the day is 60 hours long, and I can't, till he's okay with alone time, do any of that. And then, come September, I'm supposed to go back to occasional substitute teaching, 50 days over the school year.

I know: "You didn't think of this ahead of time?" I did--I figured if I got it first day of the summer break, after a few weeks he'd be fine. I'm probably just prematurely over-worrying.

Sounds like you're doing the most important thing, which is getting him used to the car.

Have you heard of the magic blanket technique for getting dogs to settle? It seems to be the hot thing in dog training at the moment, and might be useful for you if you have to leave him in other places like a sitter's house, or if you take him with you to a cafe or restaurant and just want him to hang out and be happy without your constant attention.