about that deception.free yourself from the nightmare and stop allowing him to weasel his way back into your life! Clearly he has no intention of leaving his wife when continue to accept being second fiddle.
You are not the exception to the rule. You will not cure them of cheating, because you're an awesome person. A cheater will always be a cheater. Especially, when they are cheating long into adult years.
Inner peace begins the moment you choose not to allow another person or event to control your emotions. Always take a moment to stop, breathe, and think to yourself "I can choose peace, rather than this." Always choose peace.