We will definitely be keeping Booger in our thoughts and prayers.
My vet's lab has a blood panel that includes the basic blood panel plus tick borne illnesses, you may want to see if your vet offers a similar panel. The last time I had this run in cost $85. His symptoms are fairly consistent with tick borne illness.
Here is an excerpt on Ehrlichia
"Ehrlichia canis is probably the most widely recognized tick borne disease other than Lyme disease. It is found in many areas of the world and is primarily spread by the brown dog tick. Infection rates are higher in warmer areas, so this disease tends to have a Southern distribution in the U.S. The first signs of infection with E. canis typically occur within 1 to 3 weeks after the organism enters the body. Low grade fever, decreases in platelet counts, weight loss, lymph node enlargement, lessening or lack of appetite and weight loss are the typical clinical signs. This phase of the clinical signs is often missed by pet owners and does not often cause severe enough illness to cause death. The majority of dogs manage to kill the Ehrlichia organisms during this acute phase of the infection and are no longer infected. "