I'm going to ask for antibiotics, maybe pulse treatment.
Yes, this! There are too many unknowns at this point. This will be one way to know if dental inflammation is causing resistance (perhaps with IAA's help). If yes, then getting a dental may be a possibility. But if a dental is not a good idea, I've also seen some kidney cats here, who absolutely cannot have surgery, be on pulse ABs the rest of their life. It's an acceptable option. In Neko's case, she needed a dental, but for soft tissue gum growth interfering with her eating. Unfortunately, her heart said no to anaesthesia. And there was no work around.
I would increase. If AB's help, his dose may come down when it starts to work.
I flew with Neko to Denver, then drove from there to Fort Collins, mid November. Biggest mistake was booking the return flight the weekend before US Thanksgiving.

The snow on the road from Fort Collins back to Denver wasn't fun either. But at least it was mostly flat.