Sending, receiving, and organizing email in Outlook.com
Unfortunately, the account recovery web form is the only option to recover the account. Providing as much information as possible will increase the chances of being verified through the automated process.
You may check these guidance notes on how to fill out the form through this link: https://support.microsoft.com/account-billing/guidance-notes-for-the-microsoft-account-recovery-form-4dd8fef1-33d2-4fbe-9352-66127ab9b50e
If the account recovery webform doesn't work, I'm afraid there is nothing that can be done to recover the account.
Best regards,
Darhyl