the question is should you stay for 9000 euros. the problem is that you have no guarantee that staying longer will change anything but increasing their debt. on that type of situation one must be extremely firm from the beginning, but you're probably not in that position what they perfectly know. an operator who flies with no AOC is anyway a deliquent. he has no rules and you can't deal in any way with him with your honest rules.
I would say leave a soon as possible, evaluating the measures you need to take to protect yourself against any mafia behaviour they could have. don't worry about the bond. they probably paid with fake money.