How would you expect the market's support staff to verify that you are the owner of the account? Would you want them handing over your account to any random person who submitted a ticket under another account? Put yourself in their (and everyone else's) shoes.

when I went to export the key to my persistence drive it somehow corrupted

This is why it's important to backup certain things like your keypair, passwords, links, etc.

rebooted tails only to find out that I can't access my account

Try this: Go into the persistence settings and see if the box for the GPG app became un-ticked and re-tick it (reboot may be required). This is known to happen on occasion.

I've been wanting to finalise

Worst case, I wouldn't worry too much about that. The orders will eventually auto-finalize.