So you think that YAE was working with IH to withhold money owed to you, right?
Something else is very strange about this. Brokers offer various degrees of leverage. I've NEVER heard of a broker offering a credit other than a deposit bonus. $400,000 credit on a $100,000 deposit makes no sense at all.
It also doesn't make sense that YAE would try to cheat you. Sure, $25k is a lot of money for him to grab, but that was just for 2 weeks. Unless there was something about your trading style that didn't suit him, why wouldn't he just pay you and let you make more money for him?
Was the LPOA filed with the broker in advance? Can you post it here?