Is there a way to separate informally (“Let’s try having a break from each other for a little bit, you can see the kids as much as you like!”) within the same country that you are currently in?
A friend of mine did this, as a way to test whether the guy was likely to retain interest in his kids once they were separate.
She was as sweet as pie and made it clear she’d ooze cooperation whenever he wanted to see the kids or have a zoom call…. But left it up to him to initiate the contact. Sure enough, his efforts to see and take care of the kids declined steeply. He started to settle into a comfy bachelor life of guys’nights out, porn etc., and before long she heard on the grapevine that he was seeing someone else.
After a year or so of this, she took the kids on a “holiday.” Before long, she “had” to stay a bit longer to help her parents with their garage and their garden, and oh dear, Elsie’s sprained her ankle, the doctor says she should keep it rested for a few weeks…. The guy had already more or less faded out by this point.
Eventually, when she was really sure he had moved on, she moved towards a formal legal separation.
Of course, you also have to think about the grandparents and what they are like. In the case I describe above there were already several grandchildren, so they didn’t kick up a fuss.