I think that is a wise choice. Get yourself together. Make a list of what you want to say. Leave out small things that are not violations, but bad parenting choices. Leave those for when you are interviewed. Telling your child to run away and having his mother there to try and get them to go with her? That is alarming in that what is he trying to do? I know in my discussions with a Trooper, there are things that I did not have trip me off to a big deal that they see in a different light, and that's good.
He will hang himself in all of this eventually. He's trying to wear you down. You are forming boundaries so he is trying to use your children to do it. It's sick and pathetic. Don't break. You can do this. Just keep remembering if he breaks you, the kids ultimately suffer.
I cannot even imagine. I think you need protection for yourself. Do you carry a taser or have protection for yourself? Don't freak, this is something I think all single women should do, not just you.
I also would have some tracking device on your kids besides a cell phone, which he could remove. My mom has put some sort of GPS in my dad's shoes (he has dementia), that might be a good idea. Just a thought.
Sending lots of love and light to you.