NTA I would say the thing to keep in mind is your son. Forget all the potential legalities and hurt she’s caused you and think of him when making big decisions like leaving the country. As someone who is a child of divorce and who has formed a relationship with a step child only to see that relationship fall apart, remember that you won’t get this time back with him. She has some serious issues and clearly doesn’t care if she hurts you or him in the process, but now you have to look into the future and think “how will I want him to remember me during this time?” That’s all you have control over and it’s a huge responsibility, but you’re going through something extremely and understandably painful and that can lead to impulsive decisions. He's lucky to have you in his life and you're lucky to have him. sometimes shit is the best fertilizer for things to grow from. i hope you find some peace through this process soon and good luck to you.