Hey Rob, Sorry to hear about your pup...wish things could get better for the little guy...but I know you'll do what is best.
That's too bad about the newest phase of passive-aggressive behavior from your X - though I think you're handling it the best way - staying calm, sticking to the facts, not allowing her to lure you into an interaction on her terms. I don't know if its rational or not - but my STBX seems to have the same tendency of assuming that whatever she wants for S2 is in his best interest - and so if/when I disagree, she takes it to mean that I don't have his best interests at heart. She lives according to her own little dogmatic line of reasoning.
How did she learn about your GF?
When you get a chance, would you fix the economy, please?