two weeks into adopting a 6yo lab mix from the county shelter and i feel like im messing it up, what should i actually be doing right now that i probably am not

Background. I had a dog growing up and one in my twenties, both puppies i raised, both lived their full lives with my family. I am 41 now and finally in a stable enough place to have a dog again. I went to the county shelter on a saturday with no plan to adopt and walked out with Chunk, a 6yo lab mix who had been there for 11 weeks. The intake notes said "owner surrender, moving, no behavior concerns" and the shelter staff loved him. He walked out to my car like we had been doing this for years.

It is now day 14 and i have read maybe 40 reddit threads and watched a dozen youtube videos about adult dog adoption and i still feel like i am winging it. Things that are going well, he is house trained, he eats his food, he sleeps through the night in the crate i set up next to my bed, he does not pull on the leash, he comes when called inside the apartment. Things that worry me, he barely makes eye contact with me, he has not played with a single toy ive offered, he flinches if i move suddenly when he is near me, and he spent the first 9 days sleeping in a kind of vigilant way where his eyes would crack open every time i shifted on the couch. He is starting to settle this week but i can tell he is not "my dog" yet, he is a dog living in my apartment who is waiting to see what happens.

What i am actually asking. I keep reading about the 3-3-3 rule and decompression and "the dog will tell you when he is ready" but i would love specific behavioral things to be doing and not doing in weeks 2-6 that i probably am not aware of. Am i supposed to be training him already? Should i be ignoring him more? Am i petting him too much? Is taking him on his regular morning walk through a busy neighborhood actually fine or am i flooding him? Is the no-toy thing normal? Should i try a different vet for his settle-in checkup or is the one the shelter recommended fine?

I want to do right by this dog. He has been through enough. I just dont know what i dont know yet