Opinion:
You may want to take some of your questions to the breeder from whom you got the dog. If she is a reputable breeder {whether or not she bred your particular pup}, she is sure to have opinions and experience with feeding.
Feeding, as you will soon learn, is very much a personal choice issue. You will hear from people who feed straight from the bag, who mix dry with canned, who feed only canned, who feed raw, who feed a combo of raw and kibble… the list of possibilities is endless.
And you will see that it is possible, actually probable, that your dog will have a long and healthy life, regardless of what you feed.
I think the key to longevity in dogs has more to do with being an observant owner than any particular feed. If you see your dog's coat is dull and rough, if you see the dog losing or gaining weigh in appropriately, if you see your dog with too little energy, losing hair, dry skin, etc. and then investigate possible causes -- be they food, environmental allergies, medical problem, etc.-- and work to solve those problems, your dog will be around for a very long time.