I read the history you wrote, I understand that the case you are experiencing is personal, what should have happened to you in my opinion is simple and trivial, except: you use your fiance's money to gamble and lose, then your fiancé asks for the money back and it is known that you spent the money on the Duelbits gambling site, if I judge it's not the fault of Duelbits, it's purely your own fault with your carelessness and your behavior getting caught by your fiancé.
In my opinion, it's actually easy if you ask to be blocked on the Duelbits site, you only need to delete the Duelbits gambling site web/link and all your data on your laptop or Android is complet, unless: you have been caught by your fiancé before you ask for deletion of your account on the Duelbits site or as I said above.
Conclusion: you have to swallow what you are going through right now and you apologize to your fiancé if he will forgive you, if you don't find money to cover your fiance's money, if you borrow it, if it doesn't work, just find a new girl/boy and start a new life, don't join in gambling anymore.