Potentially Moving 🙁

I moved back home to Arizona from Canada about 4 years ago. Both my sister and my mother live here in Arizona which is why I came home. Not long after relocating here I decided to get a divorce from my husband. I spent some time as a single mother before meeting my SO. When we met I lived about an hour and 45 minutes away from him in a small town where I am from. After several months of him making a tremendous effort of always driving back and forth to come stay with me on the days he didn't have his kids, we decided to move in together. Even though I did not especially want to leave my small town and my family, I made the sacrifice and moved to where he shares custody of his kids. I still see my family a fair amount so I'm okay with it. Now his ex wife wants to potentially move to another state. This is the state where they first got together and he didn't particularly want to move to Arizona in the first place, but moved here for her. They got a divorce and the rest is history and he has stayed because he shares 50% custody of his boys. He has no family and no ties here if his kids go aside from me and my family. This isn't the next state over we're talking either, this is halfway across the country. He wants to be closer to his own family which I understand but we are having a baby and I have roots here. I have always been the type to think of worst case scenario no matter what just so that I am not blindsided...my fear is that if we move and something happens down the road and for some reason we end up not being together, that I will have to abide by that State's laws and share custody with him of our own child and not be able to leave that state and come home if I want to or need to. I would absolutely hate to be stuck in a state with no family close by, by myself as a single mother of three. This is the exact situation he is in with his custody agreement here in Arizona. He never wanted to be here but then couldn't leave if he wanted shared custody of his kids. I love him and honestly don't see anything happening to our relationship in the future but I also didn't see anything happening to my former marriage 🤷 it's one of those things you just cannot predict. I would honestly go anywhere as long as we're together but I have consider all possibilities and be reasonable and realistic especially when it involves my children. Anyone have any experience with this sort of situation? Did you go?