Wanted to chime in here, as I work in the securities industry:

It is completely illegal for a broker to GUARANTEE any product. That word in particular is NEVER allowed to be used. It's even explicitly singled out in the regulations/testing that govern sales of securities.

This is actually a huge deal, and is probably why the broker was let go, as it is completely unethical. The worst part for Wells Fargo is that they can't control the actions of every single person, yet at the end of the day are completely liable for any fuck ups. I wouldn't be too hard on them- them letting the guy go and contacting you for restitution is them trying to cover their ass/correct the actions of an unethical employee.

However, you do have the right to sue/mediate in this instance. If you're interested in pursuing further, I recommend reaching out to a lawyer that specializes in securities violations (yes, these do exist). If it's not for a lot of money, it's probably easier to just take the full restitution plus whatever premium they offered you, as it will probably cost you more to go through litigation.

The bright side for you is that this will probably be reported on the guys U4, which is like background check/report card/history for a securities broker. It's essentially completely permanent, and gets checked by every financial firm that he interviews with. That will seriously fuck over his chances of getting another job in the industry again.

Now, to cover my own ass- none of this should be seen as a recommendation for any action in any direction, but merely as advice to explore on your own initiative/time.