I fully understand not being able to have certain pets due to allergies. My youngest turned out to be terribly allergic to a kitten we rescued. We had to adopt her out quickly.
I don't remember anyone saying you didn't give enough food or water, but the advice regarding the crating and not taking her outside until she's fully vaccinated came from people who have a lot of experience and knowledge.
As for the breeder not taking her back: lesson learned that a good breeder is interested in the well being of his/her pups and will have clauses about rehoming.
Can you sell her for what you paid for her? I have no clue, but my gut reaction is that if you are going to hold out for that price, you may be waiting awhile and putting your son through more suffering than he should. Only you can decide whether it's worth it or not.
Here are some links to rescues in your area if you decide to go that route:
ADOPT A PET,TUCSON,Not so Grande Dachshund & small dog Rescue,Animal shelter,no-kill,Dogs,Dachshunds, Tucson,Dachshund,Dog Boarding,Tucson,small,breed,Rescue,Arizona, Adoptions,Tucson,AZ,Australian Terrier, Beagle, Bichon Frise, Border Terrier, Cairn http://www.petfinder.com/shelters/adoptafriend.html HOPE Animal Shelter
Good luck with what ever you decide.