So this seems like you're acting on fear. You are afraid to lose your son. I have seen something similar in Andy, and at one point he was convinced I would move to Greece. It was the fear that drove the custody battle, and he had no concrete foundations for his fears.
If you wish to document your fathering, fair enough, it might do your PMA good, and I'm not saying that a father's role isn't important, it is - otherwise we wouldn't be born with 2 parents. I'm just trying to warn you not to go down the slippery slope of fighting over your child.
My DD2 ended up in therapy because of me and Andy doing this very same thing.
Do you have any proof that she would relocate? Or is it just a gut fear, or because your work mate did it? Remember, your XW is not that work mate so her actions may be different.
Can you not just be open with her and tell her you are worried about her moving and that you would no longer be allowed to have involvement with S5? Tell her you like the shared parenting arrangement and want to continue with it. See what she says. She might calm your fears, and if she doesn't, you could then document that you have stated you don't want her to move and you want to be an active parent in S5's life.
But PLEASE don't let this little boy become the reason you don't get on with each other. Andy has in the past used the children against me and even as a reason why we can't be together. I love him, I'll always love him, he says he loves me and we both love the kids, so it is a pointless waste to use kids in this way.
I suggest for the time being, don't let your imagination run riot, and if you're worried, talk to her.
I understand she says hurtful things which aren't true - but try to rise above that.
You're a good man whom I am sure does not want to get into a 'he said this, she said that' argument.
