I have an addiction as your husband. My problem was that I always thought I can handle it myself and actually never tell my partner about my problem until my rock bottom. He is really supportive just like you and I appreciate him for that. Addiction is something that need to be work on. You can not just say that this is it. I am done. The addiction will never leave you and you need to learn how to control it. He has to work on it. Has he done everything he can to get better? Counseling , treatment? Is he still taking care of his own financial?
At the end of the day , His feeling is not matter. Even though I have a sympathy for him as I am also suffering from my own addiction but If I kept failing and disappointing my partner and my family especially my kids future. I understand if my partner wants to leave me and protect our children from me and my addiction.
The question is What do you want? How do you feel? Do what is best for YOU and your children. Sure , He has problem and you stood by him. If he is still can not do or be better. You must do what is best for you.