Welcome to SR! You will find a lot of support here. Do a lot of reading and posting. We're here to support you.
To be honest, it doesn't sound to me like your husband has any intention of quitting drinking. After 4 DUIs, it should be obvious that he doesn't learn lessons easily. The thing about it is, you cannot change him and if he wants to drink, he's going to drink. You don't have to live with it though. You have the right to raise your children in a non-alcoholic home and they will be much better off for it.
Have you considered attending al-anon meetings? You will receive great face-to-face support from others who are dealing with the same issues.
Again, welcome to SR. Hope you'll stick around and absorb the wisdom you will find here.