What jurisdiction would they have in Russia or some Caribbean island? Also, Forex funds are not insured. Yeah you can sue them internationally but it would most likely be a waste of money (Russian courts...)
Agree. It's not about money itself. It's about merit and reputation. If they can steal hundred of dollars this time, they can do this to others in the future and cause much more loss.
It's a shame you now can't even try to trade your money out using a parallel counter trades account. Regarding them and how they can get away with such blatant illegal practices, given everything and possible scenarios, one should consider the possibility that the entire operation is connected to organized crime. Best thing is probably to keep your records for any eventuality and move on.
I honestly think you should just find a way to wash trade your way out of this. The problem will be on what method you'd use to guarantee one side loses vs the other. Can you buy options on anything? Have another account sell options on some ridiculously far out strike that no sane person or MM would ever hit the offer on - then hit it from this problem account.