Can I reset firmware password via Find My Mac? I would like to find out if I can set a new firmware password via Find My Mac? I already have my MacBook added but the firmware lock is active and I have no idea what it is, I've tried all combinations but they haven't worked.

If I choose to lock it using Find My Mac, will I be asked to create a new key or does that activate and expect me to enter the one it believes is already there?
No. A device technician is needed to unlock firmware. Start with online AppleCare and they can go over your options. Find My Mac just handles user account passwords.