Try to get a stool sample to a vet. If you can't find one that will work with more exotic animals, try seeing what colleges are in the area. Some have herpetology departments or even just willing biology departments. Try emailing a professor.

As for your setup:
If it is indeed a flying frog, think about the habitat it normally has. They will be fairly high up in the trees with a decent humidity and lots of air movement.

The cage should be tall with a fair amount of branches and perhaps a small computer fan to provide air circulation.

Do you have any pictures of him or your setup?
Good luck and keep us informed