It sounds to me like your wife is depressed, not in the throes of love with another man. Hopefully, her sister will be a good influence on her. I can't imagine having to take care of 5 children. certainly her days must be difficult.
I dont' know anything about the Strong Bonds program, but if they have had success with it before, then I would say you should do it. As for transparency, maybe it isn't the biggest issue. Maybe honesty is a better description of what you need from her. You can demand transparency, but someone who doesn't want to do it can still find ways to hide the contact -- new email accounts, pay as you go cellphones, secret meetings. But honesty doesn't have loopholes. You are either honest with each other or not.
I still recommend Retrouvaille. There is no particular timing on the value of the program. It helps with communication. That is a skill that is useful at any point in a marriage. Even in divorces. You could recommend Retrouvaille to your dad too. DR is the newer version of the book. It is recommended over DB.
