The amount of space that 2^67 lines of text would take up in a .txt file depends on the length of each line.
line: 20000000000000000(17 char) 1LgpDjsqkxF9cTkz3UYSbdTJuvbZ45PKvx (34 char) 17+34 = 51
total number of characters as follows:
That is the worst way to store that informacion, to store it you need to store the data in its RAW data fot the address you only need the RMD hash in raw data it is only 20 bytes.
For the privatekey there is two options, don't store the private key because you will not sort the Addresses or Store the private key because you want to Sort the addresses
If you decide to store the private key you only need 9 bytes for it... in that case you only need 29 bytes.
If you decide NOT store the private key you only need 20 bytes for the hash rmd.