Oh Emily, I really feel for you. As you know, I went through this with Leo and Penny Lane about 6 months ago. I also think getting a behaviorist out would be a good idea. I am getting ready to leave for the vet's (just a wellness check for Penny), but I will dig out the list my behaviorist gave me and post the highlights when I get back.

Quick suggestion - get on Patricia McConnells website http://www.dogsbestfriendtraining.com/home.php and see about her booklet "Feeling Outnumbered, How to Manage and Enjoy Your Multi-Dog Household" or her Dog-Dog Agression Video Set.