Right Liquidspace, that's nothing short of bullying and manipulative (as all addicts are) so at least for now you really do need to place some space between you and this man.
I disagree with with WendyS that people with addictions can't change, but he won't whilst he has you willing to feed his compulsion, so you need to make it clear that the money supply stops now. Be prepared for him to erupt and yell and be absolutely vile because he probably will.
Leave, tell him if he wants to quit gambling you are there for him, but until he does, that's it.
Stick to it.
It doesn't mean he doesn't love you that he behaves like this, just that his compulsion is overwhelming him and until he's ready to address his own addiction you'll get nowehere.
I gamble and lot, but mostly poker and long term I'm well up, so it's not the same thing and I can either gamble or not, but I have been addicted to other things and know how hard it will be for him to stop and how destructive it is for you toremain wit him whilst he's still like this.
Try and give yourself some space and sort things out so that he knows clearly there's no more money coming.
I did once lose a huge amount of money ( not gambling, through divorce) but at the end of the day it's only money, you can and will make some more and it's not the end of the world, it can be replaced. Just concentrate on getting yourself into a space where you can be happy.