Congratulations on adopting a puppy, and enjoy your puppyhood as it disappears before you even know it!
About feeding: Well the right asnwer: it depends.
Seriously, it depends largely on the quality of dog food: higher quality, less you'd need to feed your puppy. I'd strongly suggest you to start your puppy on a high-quality pet food like Wellness, Solid Gold or Nutro Ultra (they don't have the puppy chow for large breed yet). The pet food usually comes with feeding guide, you could however adjust based on your particular puppy's need.
About bathing: The less the better, particularly puppies. Their skin is so delicate, even the mildest puppy shampoo tends to destroy their natural skin moisture. Try to brush the dirt off with a soft-bristled brush or using the wipes. Also try NOT to give the puppy full bath. If you must, then use the mildest puppy shampoo with oatmeal, not human shampoo as it is way too harsh.
About flea prevention: Bathing does not prevent fleas or ticks, at least not effectively. I put my puppy on Revolution, a monthly topical applied to the back of the dog's neck, you'd need to repeat it once every month until end of October. Now some people do use flea prevention year-round, but we live in such cold place, my vet doesn't believe it's needed.
About deworming: You should put your puppy on a deworming schedule right away. Deworming include getting rid of roundworm, hookworm, ringworm and heartworm. My puppy used Bayer's Drontal, by prescription only, AND Revolution for heartworms. Your vet would be able to prescribe you with the right medication.