Lex
Your son can only be "in the middle" if you are a willing participant. Your X can't hurt you. He can try all he wants to but don't give him that "power". YOU control your emotions. YOU control whether you feel hurt or not. Really!
I picture my emotional state as a "brick". It is MY brick. And I protect that brick. If I give it to someone else, they have the power to smash me in the head with it. Hold on to your brick, Lex. (I even put little notes all over my house with the words "hold on to your brick". On the fridge, on the mirror in the bathroom, on the door to the garage where I get to my car every day. It worked for me.) And if I do allow someone access to my "brick" and they even tap me on the noggin with it, I TAKE IT BACK! (This is how I vision "detachment". I can like someone. Heck, I can even LOVE someone and not give them access to my brick.)
Don't worry about whether or not your ex and his wife forgive you or not. Who cares. What is REALLY important is that you feel comfortable with yourself and that your son isn't holding on to bad feelings about you. It is up to YOU to show him the good person you are. He's old enough and smart enough to figure out who you are. And the one who may be holding the bag on this in the end will be your X. Be patient! It'll take time for you to break down the wall that you X has built up. Only YOU have the power to do that!
The best "revenge" is success. It is also a healthy way to approach life.
YOU GO GIRL!
gentle hugs