I am a lawyer and I used to run own an office with a prop firm.
If you only made 15K gross in a year and then loss 7 thousand in a day, I would be a little suspicious of that perhaps you did not follow company rules and in a day of frustation decided to give the firm a little hit form making so much money off your commisions.
If you then threatened legal cousel and I could afford one , I would say bring it on.
What you really need to do is talk to someone in power, explain that you had an emotional blowout because of (money, bills, girlfriend, eviction, hangover, sickness, whatever that is true and provable, and say hey I really did like you guys.) What can I do to convince you of that. What would you do if you were me and wanted to get a job in the industry. Look at the postion you put me in.
Suggest a repayment schedule.
Hey if you convinced me you did not do it maliciously I would want to represent you, but if you could convince me you could probably convince them.
good luck
In the end if they are just being assholes then you get the lawyer. But that blowup does not look good to me. I know I am biased and it did happen to me for about half that by a guy who I considered a friend. I did not black mark him but part of me thought about it.