Welcome back 4my. How is your younger son reacting to the visits? Is his father treating him ok?
I find it outrageous that the courts can't put 2+2 together regarding his drinking, and his drinking and driving, not to mention coaching while under the influence. Doesn't anyone care for the children?
Please don't beat yourself up about the past. Obviously we would avoid all mistakes if we could see into the future, but you did what you thought best with the information and experience you had at the time.
I think your steadfast fight for the welfare of your children is heroic.