Hi,
I'm glad that you are already taking him/her to your vet. First thing is to get your temps up a little bit. When they are sick or have compromized immune systems it is best to keep them in the upper end of there temp range. I have been through respiratory with my rescued female last year. I used a black heat light for nocturnals and left it on her until she got better. It isn't as warm as her day temps but it took the chill of the night time drop out of the air. It's not as good but if you can't find black use red. When Eternity was sick she slept under her heat light.I made it so she could be at least 75-83.She sometimes was under it and sometimes just outside the shadow.
As far as your vet goes, look on line at: herp vet connection
look up a vet within a hour or so of you. Take down there name and phone number, then when you get to your vet ask if they would mind talking to a herp vet. This is if you feel that your vet is unsure. Just because you can't get to a herp vet doesn't mean you can't get help. If you vet even sees some reptiles a good reptile vet should be able to walk them through any questions. Some vets charge a fee for this some don't it depends on how much of there time it takes.Remember when it comes to medication it is best if your vet if familiar.Especially if it is injectible and not oral.
You vet will have to put the little one on antibiotics probably. Temp is very important,I would still keep good humidity because it is very hard on waterdragons to be dry, they can dehydrate. You just don't want it humid and cold.Also if he/she is nervous we always take black garbage bags and tape them on the outside of their cage. This is so they don't feel over stimulated. If you have any pets as well they can't see the threat. This has worked amazing for 5 different nervous reptiles I have rescued. It gives them time to adjust to everything also try to keep the room quiet. Even if it is in your room with the door closed.
hope this helps
Wd lady