If your vet has to consult a manual before treating your animal and can't cite scientific papers or medical case studies to back up what they're saying, it's time to find a new vet . I've had vets that had to basically go into the back room and look up info on the animal I was bringing in before, but they at least had the decency to tell me that they were going outside their realm of experience...

That person has no idea what they're talking about. 80% humidity is what I use for my tropical frogs and inverts, way too high for a BP. The substrate basically has to be soaked to get it that high. 50% may be on the low side for humidity, but I doubt it would cause a problem as long as you bump it a bit during the shed cycle. 86 may be on the higher end for ambient temp; I try to have a hotspot at 90 with roughly 80 ambient temp. However, again I don't believe that would be high enough to make them sick.