You are a sweet man, only wanting what is best for you and your daughter and still your wife. Believe you are doing right for all, as you are the one seeing clearly.
Move on with your plans, whether it is separation or divorce I don’t think there is much of a difference. The marriage has been touched by this addiction and as you have wrote, you have done all you can.
As the years pass, your wife’s addiction will get worst, as it is no secret this addiction just keeps get stronger. Maybe she will eventually hit rock bottom, however there is also a chance that she will not and continue to gamble. As Velvet has written, what we think is rock bottom is not always the case for cg. My father lived in a car on and off for two years and he still gambled. This is sad, this addiction is sad, what it does to people is sad, but again the addiction is not holding the persons hands to gamble. The addict is raising their hand to gamble, they are driving, walking, taking a bus, hitch hiking, etc, to the casinos, or maxing their credit cards for online gambling.
I think it is wise that you have what ever bank statements or credit card statements to show the court of her gambling, etc. This is just to show that your wife has a problem, as the courts always like to keep families together. I would have the years you have been married outlined, along with her gambling patterns and how much she owes to the casinos, etc.
Remember to take care of you in this difficult time and remember you don’t have to justify your actions, you are really the only one who knows of the hell you have been going through.