Because you have asked for help, I'll break it down.

1. Get your own drug addiction under control. You have minor children living with you and they deserve sober parents. Before you start any "yeah...but.. arguments, get your own drug addiction under control. Your minor children deserve sober parents.
2. Decide what you want for your life and proceed from there. I think what you should want is a) a sober wife, and b) failing that, a divorce. Does that seem harsh? Living a hellish half-life with someone so confused she is having an unhealthy life with her daddy over choosing to be a sober wife and mother puts divorce as an excellent option in this situation.
3. Tell Daddy to shove his slanderous comments where the sun doesn't shine; that his over-involvement in his supposedly grown daughter's life isn't welcome; that he and his massive denial likely have contributed to the problem, depriving his grandchildren of a sober mother; but that you do not want your wife back until she is sober. Then having stood up for yourself, hang up the phone, shut the door, or walk away from the guy.
4. Tell your wife the same thing you told Daddy.
5. You cannot save a marriage that is not a marriage. If you are confused about what a healthy marriage should be, can be, you can seek out counseling to help you figure that out.
I say all this with the utmost sincerity and with the health of all of your family at heart. I also understand these steps can be difficult. But the reward will be lifelong and you and your children and your wife deserve to life healthy lives.