Sorry, the email address that you used when you set up your Firefox Account is the user name for that account - it can't be changed. You would need to set up a new Firefox Account using the new email address, but that wouldn't get you your data back. Re-installing Firefox should have automatically found your Profile with your data, and used that Profile. Unless you did more than merely re-install Firefox. Did you have another device connected to your Sync account? If so, that device would have your data. If not, you were not using Sync as intended. Sync wasn't made to be used for 'cloud' data storage or when re-installing the operating system.