This has to be incredibly frustrating for you.
If I were in your shoes, I would be very concerned with the different opinions I had received.
I would want to know that the Vet who will treat my cat comes with references from other owners of very sick cats. There is a website, set up by people who have/have had cats with a very serious chronic kidney condition, kidney failure, of recommendations for competent Vets. For me, a Vets who has the knowledge, skills and the willingness to engage with cats like that would be a Vet I would choose.
There are some such Vets in Columbus who fit that criteria and listed on that site. Personally, I think I'd try "Cats Only Vets Clinic". Anyways, have a look here
I think I would want to speak with the Vet first - your chance to interview her or him.
One suggestion I'll offer is the use of a cat sack
Another is to make every effort to keep the Vet visit a pleasant experience...e.g. you said that he loves people. Well, how about an introductory visit to the new clinic when the focus would just be to "meet and greet"...I would try to prep him by using some Feliway, sprayed on the towel in his carrier...staff will need to be prepped for the visit and prepared with suitable offerings for the visitor (!), and everybody, including the Vet, will make a big fuss over him. And, all of that should be repeated when he goes for the consult appointment.
Keep us posted!