Good morning and thank you for the opportunity to help in answering your question. Your question doesn't necessarily have a cut and dry kind of answer as it's different for each individual. Based on the detailed information you've kindly provided it sounds as though you have given your husband many, many attempts at working through his addiction problems and he's yet to do so.
I think it's more of a matter of what do you need from your life and for your children's lives. Obviously he's setting a terrible example for the children...and as they grow older it will impact them that much harder.
My initial suggestion is to speak with your husband about marriage counseling and further explain to him that you're at your wits end which it sounds as though you are. He will likely agree with you and say that he will go....so I would suggest that you have an appointment scheduled with a marriage counselor for within a few days of bringing this up to him to demonstrate the seriousness of the matter and how important it is to you that he try. My honest impression is that he likely will not go which in all honesty characterizes the fact the fact that he has no intention of stopping his drinking and other addictions you mentioned. Please accept my apologies for being so blunt but I felt it important for you to be fully aware of what to look for and the potential reasons behind it.
If he does or does not go....I would suggest that you also consider seeing a therapist for you individually to help you to identify to yourself what your needs are and if they are being met by your marriage. Should you decide to separate then you will already be in treatment as you'll likely go through an adjustment period which would be completely understandable for you to go through. This way you will have the support of your therapist to help you through this period.
I sincerely XXXXX XXXXX helps in answering your question and that you found my suggestions to be of benefit.
Please let me know if you have any further questions that I can help in answering for you as I want to ensure that I have answered your question completely and thoroughly.If you feel that I've answered your question to your satisfaction then I would greatly appreciate your clicking the ACCEPT button thereby giving me credit for the answer and suggestions I've provided to you. I hope this finds you well and look forward to your response.