Dear Callie,
I have felt the same way about my cg, who is my father. I always questioned why was it so hard for him to stop gambling. It seemed like if he had some commom sense he would but I realized he didn’t. He was consumed by his gambling which I know now has taken most of his rational thoughts away.
However, and this is a BIG HOWEVER, it still doesn’t excuse their behavior and their gambling. When someone knows they have a problem/addiction and it is clear to anyone who does because we all sense when we are in trouble or have done something wrong, he/she must seek professional help. They have to get help, they cannot expect anyone in their lives to just sit there and accept it or enable it. I have found by not doing something meaning not giving your cg consequences they have no reason to face their gambling. So, as a noncg we have to decide what we are going to do. Are we just going to let the cg gamble or are we going to stand firm with not allowing it. PERIOD!
At first I let my cg gamble, though it was literally dragging me down but I just didn’t have it in me to let him go. I was afraid and i always felt because he was my father, my own flesh and blood I needed to have a relationship with him. It got to the point where I really disliked him and his presence just made my skin crawl. So I did what I should of done all along, I ended ALL TIES WITH HIM. I spoke with him before doing so, letting him know and giving him the choice to stop gambling/getting help or I would no longer help him or talk to him. He told he to get lost and that is what I did.
I am no longer a victim of his gambling and he knows it. I feel 100% better, though this did not happen over night. It is a process but it is something that is worth its self in gold. You have to do for you and your daughter. You cannot wait for a magical moment when he will snap out of his gambling, because it will never happen. Think of your daughter, soon she will understand all of this. I know this situation may seem hopless but it is not. It can be changed by you taking steps to change this stressful life you are now living. 
Take care, we are all here to support YOU!