First I'm sorry Montana! Bad situation to be in.
I think you have a hung up-hill battle before you, the court or judge may not think so kindly in this matter. I think you need to ask yourself - what's the worst case? You left the country with your son, when you start this action will it cause your X to ask for your son because you left the country? Requiring you to move back or give him up? And requiring you to pay his legal fees? What do you have to gain and at what risk?
I was nervous about this as well, but I've spent every waking moment the last 2 days doing research on this and I was very pleased with the information I gathered. I found out that the only way my ex could have ever filed a motion against me for leaving the county is if he had a stipulation put into the custody order before the custody order took effect stating I couldn't leave the country with our son without his permission. Also, there are no times or days stipulated on the custody order for visitation which is also to my advantage and the only way a custody order can be changed is if either parent can prove neglect or abuse of the other parent, of course if one of the parent died, otherwise the custody order might as well be written in stone. I can prove neglect and abuse on my ex, but I already have custody, so my ex no longer has the ability to abuse me. Well, atleast he won't when I finally get down there and take care of business.
The worst part of this all is that he always pulls this stuff around the holidays. I haven't seen any of my support in three weeks now and it's got me in an awful spot.