I am sorry to hear you are worried about Dewey. I am a veterinarian and will do my best to help.
I have actually never heard of a cat getting cat scratch fever, only transmitting it to people, so I looked it up on a website of veterinary specialists called VIN, Veterinary Information Network. The "vast" majority of cats that get infected with Bartonella (the organism that causes cat scratch fever) do not get sick. A very few have a transient fever.
So if this were my own cat, I would probably be looking for another reason for Dewey's illness. I would check him for fever (normal rectal temperature is between 101 and 102), enlarged lymph nodes, viral diseases like feline leukemia and feline AIDS. However, I might consider treating him with tetracycline or doxycycline or minocycline for cat scratch fever and other Bartonella and other tick carried diseases, especially if he has enlarged lymph nodes and a fever.
He may also have a more common thing seen in cats that have been bitten by another cat: an abscess under the skin caused by an infected bite wound. These can be hard to find, and a cat will do what you describe: act painful, reluctant to move, resist being picked up.
Let me know what other questions you have. Rebecca