IT DOES WORK. If it's not working for you, you are doing something wrong. You may ask here but don't assume its not working as it can be clearly seen by the number of people that say it works for them .
1. You can not change the m.ail. The 5TB work as long as the account domain ends in "xkx.me". For that matter, you can't even change a LOT of the other options as those are locked by the administration. Only some options about personal info can be edited and that's it.
2. The Admins of xkx.me have access to your drive/files too WITHOUT your permission (same goes for ANY enterprise/business suite like google suite) and so... NO personal files like photos etc or bank and company info. Use it to store anything you don't mind losing in the long run.
3. For those who get the 1TB will soon be upgraded to 5TB, give it a day.
4. How long this will work depends on how each one of us behaves. If you start sharing terabytes with the entire internet... you have only yourselves to blame. Be sensible and use common reason, share with friends only and ONLY if its needed and can't find any other way. Remember to remove share rights after you are done.