Thank you for contacting Just Answer.
It might help to seek out an ADD/ADHD coach.
Remember what you said. He has ADD. This is genetic. He has no control over this. He needs also to be on medicine for his ADD. I think he needs to seek out a psychiatrist so that he could be medicated.
Sorry, this was no help at all. He's on meds
Sorry, you didn't indicate that he was on medication. You stated that what you have already tried was marriage counseling. I have no way to know whether he was on medication or not if you have not indicated as much. If the medication he is on is of no help then he should be discussing this with his psychiatrists. Then if a change in medicine is tried and that, too, is or has not worked then it seems that he would need an ADD coach.
Also, if he has just retired, he may especially not know how to manage his time --- all the more reason for an ADD coach. What city and state are you in?