He's only been home for q couple of days. Give him a little bit of time to get used to his new surroundings and people. Be generous with the treats, just like you've been doing.
Do you think it would be easier to get him outside if you put him in a harness? Sometimes Iker doesn't like going for walks, either, but I don't give him the option on staying inside. I just go so he has no choice but to follow me out the door.
He sounds wonderful and it seems like he's happy. He even plays with toys and you and your husband! Relax and he'll be fine. Of course you know this already