He won't stay quiet for long.
I just got an 8 week old puppy as well and he was very quiet and sedate for about the first six days I got him. Now that he's gotten used to my apartment, my cat, and my schedule, he's come out of his shell a
lot. Yours probably will too.
If he doesn't continue to get sick, he should be okay. He's probably just stressed about being in a new place. My pup also shook a lot during his first days here and still shakes sometimes when he gets anxious or scared. I wouldn't worry about it unless it seems to be constant.
I'm not sure about how much food to give, but splitting the dog's meals up to as many as you can manage is better for their blood sugar and digestion than feeding one large meal. Their little stomachs can only handle small amounts of food when they're this little.
