I am so sorry for all you have been through. However, how wonderful for you, your husband, and your children that you fought so hard for your own sobriety and have overcome addiction yourself. Well done!
As hard as it is, you are being used. Your own father is at this point immersed into his addiction and it is going to come first. You have to stop giving him chance after chance. Protect yourself and your children at all costs. Your father is a grown adult. There is help out there for him, and he knows that. However, you cannot make him choose to be clean. He has to want that for himself.
Sending you a big hug. I am glad you are here.