Caulking = Proflex RV sealant.
Positive pressure test = go to SealTech's website and look to see if they have someone local to you.
Finally, the garden hose would not have necessarily identified the leak. This is because ambient conditions effect seal size so it could open up more in the cold for instance. Also, we engineers have shown that a hose cannot mimic rain very well, and it's why we build rain booths for testing!
You'll get this sorted and be a happy camper again! Hit those books!