I feel your pain. I only wish you peace and strength to survive this agony.
Even though its not your problem he is forcing the problem onto you.
Have you researched gambling as a way to understand all the ramifications. It may offer you tools in which to help yourself and to understand the addiction.
try support groups in your community. Help him understand his addiction and get him to put barriers in place. Control the money flow. Have his paychecks go to paying specific bills, take away credit cards and debit cards telling him to do this to save his family perhaps.
It is unfair of him to leave you feeling like you want to take your own life and you deserve better. If these things fail leave and show your girls that they deserve better too. Knowing the facts about this disease and helping your girls with the knowledge might be useful too as long as are old enough to understand. hoping for better times ahead xo