Kevin, please, be fair to all of you. OW has been smart and understanding: she does not want to break up your M and your son's family. Do not risk getting into a R on the rebound.
Give your M your best try. You have nothing to lose. I understand your not trusting your W and your need for love and understanding. But be patient and give it your best shot: if it works, you will have saved your family and have a better and stronger M. If it does not work, you will know you did your best and the M was not salvageable, but you will not wonder about that 'what ifs.'
In any case, give yourself time to heal before entering into any type of R. We discussed that in detail last year on IM. Any W deserves a partner who is free to really love her, not divided or with doubts.
"You don't throw a whole life away just 'cause it's banged up a little"
Tom Smith in "Seabiscuit"