First take a deep breath and try to calm down. Next check out the threads on Midlife Crisis. Your wife is in the prime age group. I will post more later as I am on the way out to meet some friends.
I have been dealing with this for over 2 years and H has been moved out for 15 months. It is rough but you will get through it. There are a lot of great people on this site to help you.
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.