Who told you that? 1 with 77 zeroes behind it is just 1, doesn't matter how many 0 you add behind it, the total number of keys is called N, go search for it, it is also the private key for the end range key -1.
What are you talking about? 100 is greater than 10, and 1000 is greater than 100. Obviously, the number of zeros behind the 1 matters.
Bitcoin has approx this many possible private keys:
100000000000000000000000000000000000000000000000000000000000000000000000000000
Whatever that number is called. A private key is a 32 byte array, and that above number is how many possible combinations a 32 byte array has. It's basic math.