To my mind a good vet will listen to you. You know the animal better than they do they will take the time to explain what they are doing and why and will ask for your help and question you about the animal.
Ceftazidime is a newer antibiotic as we know from human medicine bacteria become resistant to antibiotics and they need to be changed up fairly often to be effective. The treatment systems vets typically use are broad spectrum antibiotics where they are guessing and hoping that it will work on the particular bug. Pointed ones where the exact bug is tested and known and an exact match to best combat it can be found. It is best to know thine enemy.
Never be self conscious about asking questions! Do not regret that you failed to ask something when you should have. Multiple sources too don't just blindly take my or anyone else's word for something back it up with a second and third source.
Good luck with your snake! Make sure you trace down the possible issues that may or may not have made the RI appear in the first place as well.