Any kind of service that asks you for a fee to be paid before they send you the money is a scam!
Why would they ask you to pay 0.75% or whatever when they could simply subtract that from the money they owe you, right?

As for your gains, it's just as LeGaulois said, those were probably never there, they manipulated trades to show you a positive balance, trying to get you to invest more and more and by the time you actually want to cash out it's either that they ask you for more money like in your case, they go silent for others, or somehow your account just makes a few wrong trades and you get liquidated since it's just fake numbers they can also fake everything!

Just be careful what you do next and don't fall for any more tricks, cut your loss and be done with it, seems like they don't let you go as easy as that, after the broker scam they might try a romance scam, lol
https://www.trustpilot.com/users/625666ec613f560013adce6c