Going by what you stated, it seems they were giving you $100,000 that could not be withdrawn and could only be used to play with. Why should you consider taking $100,000 in funds you cannot
even withdraw when they owe you $300,000, you took the correct course of action by rejecting their so-called offer.
This is an interesting scam accusation against Betfury. The fact that you have decided to stand your ground and are trying to get the correct payout, deserves respect. $100,000 is a phenomenal amount of money to turn down but there is no reason why you should accept it if Betfury owe you $300,000.
I didn't inquire about the details, but the $100k wasn't offered as cash, but as a bonus, likely with very unfavorable terms.