I'm surprised he would suggest grapes...If you talk to him again, I'd mention that they're not recommended since they can cause organ failure (I believe renal failure if my memory is working right today). It's possible he just hasn't heard that it applies to hedgehogs as well, or hasn't thought about it.
Honestly, if he listened to you and didn't seem to be too rude or upset by you refusing hedgehog food or ignoring the grapes suggestion, I wouldn't write him off. Yeah, it's annoying that they may not be up-to-date on nutrition information, but a vet that's willing to listen to you and work with you is always a nice thing when it's difficult as it is to find a vet that will see hedgehogs. Listening to you regarding the blood sample & skin scraping sounds like a good thing, so he can't be too bad!
As far as the wet food, he's not far off on that - more moisture helps with processing protein, which is why too high of protein in dry food can cause kidney problems. However, it's a challenge with hedgehogs since the heat means bacteria can grow more quickly on wet food, and it also dries out and gets gross by the time it's been out a few hours. Some people find ways to work around that (a cube of wet food frozen to thaw out slowly), some hedgehogs just eat early and maybe once more when human wakes up, etc. It's up to the owner if they want to try doing wet food instead or what they prefer.
I'm not sure on the sneezing question, though, since I don't have any personal experience with URIs.
~*~*~ Kelsey ~*~*~
RIP my sweet Lily ~ 6/12/08 - 1/20/12