I totally know how you feel. I assume Jack is ok with you, and your able to pet and handle him? My new one will only occasionally let me pet him and then it's only for a few seconds before you get slapped and he tries to bite, and that's in his room where he feels safe, if he's in the rest of the house you get attacked and i cant even pick him up, he just knocked my glasses off and got me in the face with his claws. and my resident cat isn't playing or trying to sow him who is boss, she's out for blood, she has chased him down and attacked twice now, if I hadn't been right there with a blankt to throw on them, there would of been blood. It's very upsetting. I think at some point, at least in my case, you have to consider whats best for the cats involved. I don't think I want to continue trying with the new cat and risk doing damage to the relationship of the 2 cats I already have . The Prozac, my Tonkinese is on that to control his Feline Hyperesthesia and with all the noises and fighting going on with the other 2 cats and all the stress , we have had to up his dosage. The more agitated they are the less the medicine works like its suppose to, and i have read that it works differently in different cats. Please post what the specialist tells you and recommends. Good luck.