Pack you have come a long way. Keep going. The road to greatness doesn't have an end, there is no finish line. So enjoy the journey because that is all any of us has.
I don't think you have to say anything to your son about moving on. Just do it. He will see your actions and how you are showing up in the world. Remember you are an example to him of what a man is, how a man conducts himself. It's a great responsibility (no pressure LOL).
Don't get sidetracked inside your head re your ex bringing OM around the kids. You can't stop it. Accept it will happen. They have one father and that's you my friend. Be the man. There are ways to deal with any negative influences that OM and/or your ex have on the kids. I have some experience with this re my ex. The good people on this board will provide direction if that happens. Unless and until it does, don't worry about. Be a strong and dominant role model and influencer yourself such that others pale in comparison.
