I'm sorry to learn of your situation and the dilemma you face.
Your ex can only take your child to live abroad with either your consent, or permission from the court. She can't just up and leave. It is unlawful to remove a child from the UK without either your consent , or leave (permission) from the Court - it is child abduction. If you don't consent she will need to apply to court. Alternatively, you could apply for a Prohibited Steps Order to prevent her from taking your child to live abroad.
What connection does your ex have with the intended country? Do you know when she is likley to attempt to relocate?
Do you want to continue to have a relationship with your son? Do you want your son to know you, to have his father in his life? If so, then you need to consider fighting this relocation.
If your ex needs to apply to court, she would need to show that the relocation is in the best interests of your child, that the move would offer your child opportunities, family relationships and a lifestyle that isn't on offer should he remain living in the UK. You would need to show that the move would be detrimental to your child, that it would severely impede on his relationship with you.
Try not to look at this through the gendered lens you are currently using, and look at what you strongly believe is best for your child - if you want to be in each other's lives and have a relationship with each other, then fight this, fight it with everything you have.
However, if you believe that him moving away would be in his best interests, it is important to try to agree some sort of contact arrangements with his mother before they leave. This can include regular phone/video calls as well as actual time together, either here or in the new location.
Should you "ghost" your son? My advice would be no - unless staying in his life is something you cannot do. He is far too young to understand why you wouldn't be part of his life after moving.
If you want to discuss your options, you are welcome to call the Wikivorce helpline and ask for a free 20 min call with the child issues consultant.
Please talk to your GP about how you are feeling, and the Samaritans provide non-judgemental, free support on 116 123 24 hours a day.