Unfortunately unless you have valid proof of purchase showing your name and the system serial number, then there is nothing that can be done if you don't recall the firmware password. Contact your local Apple Store or Apple Authorized Service Provider to find out exactly what paperwork they will accept for valid proof of purchase. If you purchased it directly from Apple, then Apple may still have that information. Unfortunately an AppleID only means you have current control of the laptop, but it does not imply official owner.
Without a firmware password or without disabling the firmware lock you will be unable to boot to any external media.