You did not cause this. You cannot control this. You cannot cure this.
You are not powerful enough to send him back to the pipe just as you have no power to keep him off it.
It's not personal. It just feels that way, right now.
No one can continue to lie, cheat, steal and manipulate us unless we let them do so. I cannot imagine reestablishing trust after all that came before. I could not imagine someone like this in the same house with my children. That's me. Only you can decide your own bottom with all of this.
That you are sending him calling cards and writing letters intended to compel him to snap out of it and become the man you thought he was is codependency 101. The root of all codependencyis ego and a belief that we have control over other people. Everything else is rationalization
(excuse).
Consider picking up a copy of Codependent No more by Melody Beatie. It's at your loacal library and used on Amazon. It has the power to help you change your life.