I have never posted to you before but have read your insight on other threads (maya, GBO, H2H). I am so sorry for your latest news about S and D. I can understand your worry. In most cases, smoking pot at that age is just experimental. But I can understand your concern for D. I have not had this concern as far as my children are concerned. However, my intelligent, mature husband has a 20 year daily marijuana habit that causes me great concern and because he is a stubborn adult male , I have not found a solution. The consequences of your children's actions will probably be enough to stop the behavior.
Thank you for your helpful summary of your journey with your H, it is an inspiration to those of us who were thinking of throwing in the towel.
Everything happens for a reason, maybe Dad needs to find that it isn't better out there, he needs to realize how good he had it here. Maybe he will find God and that is the most important thing when he finds Him he will know he is supposed to come home.