Having an excessive bankroll in gambling wouldn't stop you from having a limit to the resources that you gamble with. If you don't have an amount set aside for gambling you will stake above your means without realizing yourself. Most people don't know how easy it is to gamble with a thousand dollars, that money can be everything you have and it can be exhausted in a Twinkle of an eye. The More you keep funding in the process of chasing your losses the more you keep throwing all your money away. Having an excessive bankroll doesn't mean that it's inexhaustible.
Sure, an excess bankroll is exhaustible. The issue at hand is he really didn't want to have that excess bankroll and looking for a way to withdraw it, but since he has to wager according to the casino, then I will suggest he doesn't exceed his $100 budget, maybe for the month or however, he planned to spend it . He just shouldn't exceed it, no matter what.
Responsible gambling should come in handy here because in a twinkle of an eye, one $1000 can be used to stake, and before you know, it's gone.
Once he exhausts the $100, he should go on to play freerolls or any other game, but shouldn't touch his balance again.