First of all, Hi! and welcome to the forum.
Second of all, congratulations on your wins!!
From what I've read and without knowing which casino this is and knowing exactly what their terms are I guess all you can do is to speak to support to see if they will now authorize bigger withdrawal limits considering the amount you have just won. Other than there there really doesn't seem like there is much more you can do but to withdraw at those limits and wait for it all to arrive. It's funny as we've been discussing this lately. Don't self exclude whatever you do.
If you are told you have to wait to get your withdrawals based on this limits you have to make sure you stay strong and don't wager away what's left in your account while you are waiting. Chances are you are just going to lose if you do.
So, the first withdrawal has been received in your chosen payment method? I would suggest they are now carrying out additional checks considering the amount. Is it a reputable casino you are in?