Is this still on-going because it looks like they are confused as to what your problem is. No key is generated upon creating an account? So I'm unsure why they're asking for any such information. The best you can do, is take as many details as you can remember and forward them.
Such as your old email address (active or not)
Any username you had possibly used
Date of birth (because I'm sure you have to put it in when you sign up?)
Maybe an approximate on the amount of games you have bought
Roughly how long you have held the account?
I would respond to the ticket, expressing your confusion to their response, reiterate your problem and forward the info above. Maybe they can take something from that and identify it.
Beyond that, its abandoning it and starting anew.
__________________
|