First of all welcome to YT and congratulations on your new furbaby! I let my furkids sit in my lap when we picked them up which is a no no. I should have had them in a crate because they would have been safer and because Tucker got carsick all over my lap
Bring a few treats with you and if you lead him in there with one you will hardly be forcing him. He might whine for a while, but I'm sure he'll calm down after a little bit.
I would keep him confined to one room for a while so he's not overwhelmed and so you can keep an eye on his potty dance. It's never to early to start potty training so I would say, yes, taking him out every hour would be ideal until his bladder has time to grow and until he gets the general idea that he should potty outside. There will be accidents though so invest in some good cleaner such as Nature's Miracle that can be found at nearly any pet store.
On the collar, he should only wear one for identification purposes. For no reason should you attach his leash to it. A harness is the best things for dogs this tiny. They have very delicate tracheas and shouldn't have extra pressure on them from a collar attached to a leash. This can cause a problem called collapsed trachea, which from it's name you can tell is not a good thing. Good luck with everything and if you need anything feel free to pm me!