I get the impression that this is "history repeating itself" from your comment about your parents 20 years ago . Were you a mother at the same age ? I've often noticed that our adult children can repeat history like this, having babies at the same age as their parents did.
There isn't anything you can do at the moment. He is living in another country, and maybe he is happy despite the misgivings that you express. I've been in the same predicament , and there isn't anything you can do but wish them well and let them get on with it.
Re your later comment about "venting" to someone who then rang DS, well you can't undo that mess. I'd stop trying to apologise, since it won't get you anywhere. Maybe give it a few days and then send a text saying that if there is anything you can do, or help them with, to let you know....and leave it at that.
You say you've been close in the past - well you can be close again, but his life is changing and there is someone else in his life now. And soon there will be a child who will make you a grandmother (whether you feel old enough or not ! ) . I'd suggest treading carefully , and stop judging his partner because she is going to be part of his life, and yours, forever now.
As a grandparent you have to get used to the idea that you will never again be at the centre of your child's life. His partner and his child will be in that position and you'll be out on the periphery . Once you accept that role , life gets easier because you stop grieving for your past relationship. Take care of yourself, OP.