I want to caution against keeping him on the Vetoryl. This is a VERY powerful drug and can cause permanent damage to the adrenal glands and even death. Since there are enough red flags to make that "borderline" diagnosis suspicious he needs to be off that drug. I would stop it now and not even think about restarting it until he's had plenty of time to get settled into his new home and the heartworms cleared. Then, and ONLY then, if he is displaying the signs I gave you above would I consider having the testing done. But please do stop giving the Vetoryl for now.