Each and every Catholic on this earth has some teaching that they struggle with or that they break, that is why it is called “practicing” Catholicism. Those who have perfected it earn the title “Saint”
We are supposed to help our brothers and sisters, especially the brother or sister we married, to get to heaven. This man sees his wife struggle and he himself is struggling, we can and should help them. We can be a loving example of Christ and the teaching of Holy Mother Church. We would be ill advised to go to either extreme, shrugging his shoulders and saying as Puddy said to Elaine “I’m not the one who is going to hell” or becoming tyrants.
My guess is that this is not as much about contraception and NFP as it is a family overwhelmed with life. Maybe wife is living far from her family and she feels isolated and alone, something as simple as having a “mother’s helper” for a couple of afternoons, Dad taking the kids every other Saturday so she can go have some down time, hiring a housekeeper to come in once each week.
If I were a betting man, I’d venture there has not been “date night” for a long time. Get a sitter and go to an art museum or the symphony or just to a restaurant where there are not blaring TVs on the walls. Find each other again. Remember why you fell in love in the first place.
I’d suggest that a retreat like Retrouvaille would be worth a shot.
Another is a book called “A Sinner’s Guide to Natural Family Planning”.
Last suggestion, a 2 part video series called “Beloved”. The first is aimed at those who plan to get married, but, it is very good for us long married folks. The second part is aimed at living out marriage. They are part of the Formed.org subscription. Well worth the monthly subscription fee!!