I am so sorry to hear about Tatum!
Both of my girls do not like to ride in the car, Bailey likes to hideout under the seat
and Angel gets carsick.
I have found that giving Angel a couple of drops of Rescue Remedy
(holistic anxiety drops) a half hour before leaving in the car really helps calm her.
I also put both in their kennel together when we travel with a comfy soft blanket and it really helps. (No, Bailey is not allowed to ride under the seat)
Good luck in your search for the perfect doctor.
Sending Prayers & Angels to Tatum & your family.