1)No, a fertilized egg is not healthier than a non-fertilized egg and vica-versa. And, the eggs you buy from the store are not fertilized, because egg farms only keep hens, so the eggs won 't become fertilized.
2)Many people say that a fertilized chicken egg is more healthy. However, this is not true as both types of eggs are healthy and have almost same nutritional value. Eggs are one of the healthiest food, and good for people of all ages. But, if you store any egg for long, then it will start to lose its protein content. Also, if fertilized eggs are stored in the fridge, then they will not hatch.