Chris, sorry to hear stuff like this again.
1. You called a lawyer already, Good! Definately track him down for back support.
2. CALL exmil ASAP!! If anyone else treated Britt like that, say a teacher, you wouldn't write a letter!! CALL HER and tell her she will discontinue her verbal abuse towards Britt or, she won't see her again. There is NOTHING that gives exmil that visitation AND, even if she had the right, I'd be calling a lawyer to get it stopped based upon the abuse & harassment.
My decree states that neither party shall speak unfavorably about the other, including support issues so why, in God's name would anyone else be allowed to do that? Grand-mama must stop immediately!
Her visits, if they continue, should be of a much more happier nature.
Sorry, I'm done now. That exmil just inflamed me, that's all!
{{HUGS}} fou you & Britt!