Welcome to YT Jim!! I have a Shi Tzu AND a Yorkie in two dogs. You got them both together! The best of two breeds.
I think you're not dealing with two different, although normal, issues. Puppy biting is very normal. They have to learn either a) not to bite at all, or b) how much pressure to use. Just the other day, I was playing with Coby and was amazed to suddenly realize he has learned the perfect bite pressure (unless we're both grabbing for the same time of course!
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The growling/snapping part is a different issue, and it sounds like you're trying to deal with the dominance/pack leader thing.
8 weeks old is very young. So stay steady. Several weeks of hard work pays off with YEARS of happy co-existance and love.
Best of luck. Can't wait to hear more. And I'd love to see a picture. My two favorite breeds!!