welcome B Worgan!! I too rescued a dog and it has taken almost 5 months for her to slowly overcome her separation anxiety, and even now she sometimes relapses. Raimnbow offered some really good ideas- stuffed Kong, and only leaving for short trips. You should also look into crate training if you haven't already, and don't make a big fuss about saying goodbye, or hello when you come home.
Sorry-
but I do have something to say about
Rescue Remedy- I use it for myself!
I am a nervous sleeper when hubby isn't home, so I take a couple sprays before I go to bed and it seems to help me fall asleep without any anxious/ scared feelings.