Hi welcome to Yorkie Talk
Well, technically he's too young to be away from his mom at 6 weeks old (ideally he should have had another 6 more weeks yet with her) so you have a really baby puppy on your hands.
I honestly wouldn't take him outside really at all unless he was in your arms for a few more weeks yet.
Puppies shouldn't, as a rule of thumb, be around other dogs or out walking where other dogs could have been until they've had their last puppy shots at around 4-5 months old (rabies vaccine might not be given till a month later than that, but you're ok there as long as you're not going hiking in the woods or something
). Your vet was definatly right not to give him more than one vaccine at a time and you should actually keep doing it that way his whole life, it's just safer. Just wait for your vet to give you the ok before you take him around other dogs or walking through the neighborhood.
Good luck and congrats on your new baby