My daughter ate like seriously all the the time when she was just a few weeks old it was non stop. And all so sneezing is normal for them it freaked me out in the beginning also. And as for being stuffy she may just have allergies. She is most likely fine there sinus are very tiny. Just clean her nose out often. Or call ur doc if ur really worried
My midwife told me tht breastfeedin at th start is very demanding and baby cld want to eat every hr until ur milk fully comes in. So i would say its totaly normal.
The eating sounds like a little growth spurt is all.
And the sneezing and all could be an allergy to something in the home or clothes. But address it with her pediatrician because she is so new :)