you seem to be a threat to them you only deposited less than $100 worth of ETH and you have made it to $500, that is 5x you could be draining all their funds in no time if they still allow you to play. i'd like to copy bet.
it is unfair though that they take your winnings since you won all those before the change of terms and conditions. they have decided though, nothing else can be done but maybe the AG can do something for you.
If he deposited the minimum required amount of fund in the site to play the game then they have no excuse to freeze or stopped his account. Or he deposits $10 which is the requirement for many casinos this days and win big then they have to pay him and allow him to withdraw his money and if they don't want him to continue with them then they should pm him and explain things to him and stop him instead of banning him suddenly like that.
From the evidences the op presented here, I don't think winz.io did well for this issue. I take winz.io as one of the best casinos in the forum so if they do one kind, they might lost their trust from me. They have to be fear in their dealing with participants and their clients.