I'll reply before I read everyone else's replies. Get the book "divorce poison". Read it. It has some suggestions. YES, suggestions even for children who are adults and living far away. You'll find amazing hope and understanding in it.
You'll want to understand the concept, if you don't already, of parental alienation syndrome. And the trick is to figure out how to let them know that they don't have to choose between the two of you, even if they made a choice long ago, this is not like a sporting event where you have a winner and loser and can root for the underdog or home teem. It's not like a war where you enlist others to fight the battle. I know it's been played like that so far, but if you calm down, stop with the talk of ulcers and unfair settlements, and start making sense out of what has happened, understanding that it happens to lots of people and there may be some ways so rebuild, even though it's tougher when theyr'e adults because building a normal adult realtionship with kids is a challenge in the first place... you can do this.
Start by getting a copy of that book, Divorce Poison. You may soon find yourself getting another copy and sending it to your son... not as a slap upside the head, but rather a hug and an olive branch that will say to him "there's stuff that happened that you will never know about and never should, and it's wrong for you to take sides and make choices just becasue of waht your Dad said about me. I still love you and Im here when you want to talk".