It sounds like you've done all you can. This may sound silly but it always works for my dogs when they and I are stressed. I can't sing my way out of a paper bag but they don't mind if I quietly sing one of their silly songs to them. Even better, I will read to them out of a book. Just the sound of your voice will calm them - and you when you look into their trusting eyes. Silly I know, but it works for me